rpmalloc/rpmalloc.c

/* rpmalloc.c  -  Memory allocator  -  Public Domain  -  2016-2020 Mattias Jansson
 *
 * This library provides a cross-platform lock free thread caching malloc implementation in C11.
 * The latest source code is always available at
 *
 * https://github.com/mjansson/rpmalloc
 *
 * This library is put in the public domain; you can redistribute it and/or modify it without any restrictions.
 *
 */

#include "rpmalloc.h"

////////////
///
/// Build time configurable limits
///
//////

#if defined(__clang__)
#pragma clang diagnostic ignored "-Wunused-macros"
#pragma clang diagnostic ignored "-Wunused-function"
#elif defined(__GNUC__)
#pragma GCC diagnostic ignored "-Wunused-macros"
#pragma GCC diagnostic ignored "-Wunused-function"
#endif

#ifndef HEAP_ARRAY_SIZE
//! Size of heap hashmap
#define HEAP_ARRAY_SIZE           47
#endif
#ifndef ENABLE_THREAD_CACHE
//! Enable per-thread cache
#define ENABLE_THREAD_CACHE       1
#endif
#ifndef ENABLE_GLOBAL_CACHE
//! Enable global cache shared between all threads, requires thread cache
#define ENABLE_GLOBAL_CACHE       1
#endif
#ifndef ENABLE_VALIDATE_ARGS
//! Enable validation of args to public entry points
#define ENABLE_VALIDATE_ARGS      0
#endif
#ifndef ENABLE_STATISTICS
//! Enable statistics collection
#define ENABLE_STATISTICS         0
#endif
#ifndef ENABLE_ASSERTS
//! Enable asserts
#define ENABLE_ASSERTS            0
#endif
#ifndef ENABLE_OVERRIDE
//! Override standard library malloc/free and new/delete entry points
#define ENABLE_OVERRIDE           0
#endif
#ifndef ENABLE_PRELOAD
//! Support preloading
#define ENABLE_PRELOAD            0
#endif
#ifndef DISABLE_UNMAP
//! Disable unmapping memory pages (also enables unlimited cache)
#define DISABLE_UNMAP             0
#endif
#ifndef ENABLE_UNLIMITED_CACHE
//! Enable unlimited global cache (no unmapping until finalization)
#define ENABLE_UNLIMITED_CACHE    0
#endif
#ifndef ENABLE_ADAPTIVE_THREAD_CACHE
//! Enable adaptive thread cache size based on use heuristics
#define ENABLE_ADAPTIVE_THREAD_CACHE 0
#endif
#ifndef DEFAULT_SPAN_MAP_COUNT
//! Default number of spans to map in call to map more virtual memory (default values yield 4MiB here)
#define DEFAULT_SPAN_MAP_COUNT    64
#endif
#ifndef GLOBAL_CACHE_MULTIPLIER
//! Multiplier for global cache
#define GLOBAL_CACHE_MULTIPLIER   8
#endif

#if DISABLE_UNMAP && !ENABLE_GLOBAL_CACHE
#error Must use global cache if unmap is disabled
#endif

#if DISABLE_UNMAP
#undef ENABLE_UNLIMITED_CACHE
#define ENABLE_UNLIMITED_CACHE 1
#endif

#if !ENABLE_GLOBAL_CACHE
#undef ENABLE_UNLIMITED_CACHE
#define ENABLE_UNLIMITED_CACHE 0
#endif

#if !ENABLE_THREAD_CACHE
#undef ENABLE_ADAPTIVE_THREAD_CACHE
#define ENABLE_ADAPTIVE_THREAD_CACHE 0
#endif

#if defined(_WIN32) || defined(__WIN32__) || defined(_WIN64)
#  define PLATFORM_WINDOWS 1
#  define PLATFORM_POSIX 0
#else
#  define PLATFORM_WINDOWS 0
#  define PLATFORM_POSIX 1
#endif

/// Platform and arch specifics
#if defined(_MSC_VER) && !defined(__clang__)
#  ifndef FORCEINLINE
#    define FORCEINLINE inline __forceinline
#  endif
#  define _Static_assert static_assert
#else
#  ifndef FORCEINLINE
#    define FORCEINLINE inline __attribute__((__always_inline__))
#  endif
#endif
#if PLATFORM_WINDOWS
#  ifndef WIN32_LEAN_AND_MEAN
#    define WIN32_LEAN_AND_MEAN
#  endif
#  include <windows.h>
#  if ENABLE_VALIDATE_ARGS
#    include <intsafe.h>
#  endif
#else
#  include <unistd.h>
#  include <stdio.h>
#  include <stdlib.h>
#  include <time.h>
#  if defined(__APPLE__)
#    include <TargetConditionals.h>
#    if !TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
#    include <mach/mach_vm.h>
#    include <mach/vm_statistics.h>
#    endif
#    include <pthread.h>
#  endif
#  if defined(__HAIKU__)
#    include <pthread.h>
#  endif
#endif

#include <stdint.h>
#include <string.h>
#include <errno.h>

#if defined(_WIN32) && (!defined(BUILD_DYNAMIC_LINK) || !BUILD_DYNAMIC_LINK)
#include <fibersapi.h>
static DWORD fls_key;
#endif

#if PLATFORM_POSIX
#  include <sys/mman.h>
#  include <sched.h>
#  ifdef __FreeBSD__
#    include <sys/sysctl.h>
#    define MAP_HUGETLB MAP_ALIGNED_SUPER
#    ifndef PROT_MAX
#      define PROT_MAX(f) 0
#    endif
#  else
#    define PROT_MAX(f) 0
#  endif
#  ifdef __sun
extern int madvise(caddr_t, size_t, int);
#  endif
#  ifndef MAP_UNINITIALIZED
#    define MAP_UNINITIALIZED 0
#  endif
#endif
#include <errno.h>

#if ENABLE_ASSERTS
#  undef NDEBUG
#  if defined(_MSC_VER) && !defined(_DEBUG)
#    define _DEBUG
#  endif
#  include <assert.h>
#else
#  undef  assert
#  define assert(x) do {} while(0)
#endif
#if ENABLE_STATISTICS
#  include <stdio.h>
#endif

//////
///
/// Atomic access abstraction (since MSVC does not do C11 yet)
///
//////

#if defined(_MSC_VER) && !defined(__clang__)

typedef volatile long      atomic32_t;
typedef volatile long long atomic64_t;
typedef volatile void*     atomicptr_t;

static FORCEINLINE int32_t atomic_load32(atomic32_t* src) { return *src; }
static FORCEINLINE void    atomic_store32(atomic32_t* dst, int32_t val) { *dst = val; }
static FORCEINLINE int32_t atomic_incr32(atomic32_t* val) { return (int32_t)InterlockedIncrement(val); }
static FORCEINLINE int32_t atomic_decr32(atomic32_t* val) { return (int32_t)InterlockedDecrement(val); }
static FORCEINLINE int32_t atomic_add32(atomic32_t* val, int32_t add) { return (int32_t)InterlockedExchangeAdd(val, add) + add; }
static FORCEINLINE int     atomic_cas32_acquire(atomic32_t* dst, int32_t val, int32_t ref) { return (InterlockedCompareExchange(dst, val, ref) == ref) ? 1 : 0; }
static FORCEINLINE void    atomic_store32_release(atomic32_t* dst, int32_t val) { *dst = val; }
static FORCEINLINE int64_t atomic_load64(atomic64_t* src) { return *src; }
static FORCEINLINE int64_t atomic_add64(atomic64_t* val, int64_t add) { return (int64_t)InterlockedExchangeAdd64(val, add) + add; }
static FORCEINLINE void*   atomic_load_ptr(atomicptr_t* src) { return (void*)*src; }
static FORCEINLINE void    atomic_store_ptr(atomicptr_t* dst, void* val) { *dst = val; }
static FORCEINLINE void    atomic_store_ptr_release(atomicptr_t* dst, void* val) { *dst = val; }
static FORCEINLINE void*   atomic_exchange_ptr_acquire(atomicptr_t* dst, void* val) { return (void*)InterlockedExchangePointer((void* volatile*)dst, val); }
static FORCEINLINE int     atomic_cas_ptr(atomicptr_t* dst, void* val, void* ref) { return (InterlockedCompareExchangePointer((void* volatile*)dst, val, ref) == ref) ? 1 : 0; }

#define EXPECTED(x) (x)
#define UNEXPECTED(x) (x)

#else

#include <stdatomic.h>

typedef volatile _Atomic(int32_t) atomic32_t;
typedef volatile _Atomic(int64_t) atomic64_t;
typedef volatile _Atomic(void*) atomicptr_t;

static FORCEINLINE int32_t atomic_load32(atomic32_t* src) { return atomic_load_explicit(src, memory_order_relaxed); }
static FORCEINLINE void    atomic_store32(atomic32_t* dst, int32_t val) { atomic_store_explicit(dst, val, memory_order_relaxed); }
static FORCEINLINE int32_t atomic_incr32(atomic32_t* val) { return atomic_fetch_add_explicit(val, 1, memory_order_relaxed) + 1; }
static FORCEINLINE int32_t atomic_decr32(atomic32_t* val) { return atomic_fetch_add_explicit(val, -1, memory_order_relaxed) - 1; }
static FORCEINLINE int32_t atomic_add32(atomic32_t* val, int32_t add) { return atomic_fetch_add_explicit(val, add, memory_order_relaxed) + add; }
static FORCEINLINE int     atomic_cas32_acquire(atomic32_t* dst, int32_t val, int32_t ref) { return atomic_compare_exchange_weak_explicit(dst, &ref, val, memory_order_acquire, memory_order_relaxed); }
static FORCEINLINE void    atomic_store32_release(atomic32_t* dst, int32_t val) { atomic_store_explicit(dst, val, memory_order_release); }
static FORCEINLINE int64_t atomic_load64(atomic64_t* val) { return atomic_load_explicit(val, memory_order_relaxed); }
static FORCEINLINE int64_t atomic_add64(atomic64_t* val, int64_t add) { return atomic_fetch_add_explicit(val, add, memory_order_relaxed) + add; }
static FORCEINLINE void*   atomic_load_ptr(atomicptr_t* src) { return atomic_load_explicit(src, memory_order_relaxed); }
static FORCEINLINE void    atomic_store_ptr(atomicptr_t* dst, void* val) { atomic_store_explicit(dst, val, memory_order_relaxed); }
static FORCEINLINE void    atomic_store_ptr_release(atomicptr_t* dst, void* val) { atomic_store_explicit(dst, val, memory_order_release); }
static FORCEINLINE void*   atomic_exchange_ptr_acquire(atomicptr_t* dst, void* val) { return atomic_exchange_explicit(dst, val, memory_order_acquire); }
static FORCEINLINE int     atomic_cas_ptr(atomicptr_t* dst, void* val, void* ref) { return atomic_compare_exchange_weak_explicit(dst, &ref, val, memory_order_relaxed, memory_order_relaxed); }

#define EXPECTED(x) __builtin_expect((x), 1)
#define UNEXPECTED(x) __builtin_expect((x), 0)
    
#endif

////////////
///
/// Statistics related functions (evaluate to nothing when statistics not enabled)
///
//////

#if ENABLE_STATISTICS
#  define _rpmalloc_stat_inc(counter) atomic_incr32(counter)
#  define _rpmalloc_stat_dec(counter) atomic_decr32(counter)
#  define _rpmalloc_stat_add(counter, value) atomic_add32(counter, (int32_t)(value))
#  define _rpmalloc_stat_add64(counter, value) atomic_add64(counter, (int64_t)(value))
#  define _rpmalloc_stat_add_peak(counter, value, peak) do { int32_t _cur_count = atomic_add32(counter, (int32_t)(value)); if (_cur_count > (peak)) peak = _cur_count; } while (0)
#  define _rpmalloc_stat_sub(counter, value) atomic_add32(counter, -(int32_t)(value))
#  define _rpmalloc_stat_inc_alloc(heap, class_idx) do { \
	int32_t alloc_current = atomic_incr32(&heap->size_class_use[class_idx].alloc_current); \
	if (alloc_current > heap->size_class_use[class_idx].alloc_peak) \
		heap->size_class_use[class_idx].alloc_peak = alloc_current; \
	atomic_incr32(&heap->size_class_use[class_idx].alloc_total); \
} while(0)
#  define _rpmalloc_stat_inc_free(heap, class_idx) do { \
	atomic_decr32(&heap->size_class_use[class_idx].alloc_current); \
	atomic_incr32(&heap->size_class_use[class_idx].free_total); \
} while(0)
#else
#  define _rpmalloc_stat_inc(counter) do {} while(0)
#  define _rpmalloc_stat_dec(counter) do {} while(0)
#  define _rpmalloc_stat_add(counter, value) do {} while(0)
#  define _rpmalloc_stat_add64(counter, value) do {} while(0)
#  define _rpmalloc_stat_add_peak(counter, value, peak) do {} while (0)
#  define _rpmalloc_stat_sub(counter, value) do {} while(0)
#  define _rpmalloc_stat_inc_alloc(heap, class_idx) do {} while(0)
#  define _rpmalloc_stat_inc_free(heap, class_idx) do {} while(0)
#endif


///
/// Preconfigured limits and sizes
///

//! Granularity of a small allocation block (must be power of two)
#define SMALL_GRANULARITY         16
//! Small granularity shift count
#define SMALL_GRANULARITY_SHIFT   4
//! Number of small block size classes
#define SMALL_CLASS_COUNT         65
//! Maximum size of a small block
#define SMALL_SIZE_LIMIT          (SMALL_GRANULARITY * (SMALL_CLASS_COUNT - 1))
//! Granularity of a medium allocation block
#define MEDIUM_GRANULARITY        512
//! Medium granularity shift count
#define MEDIUM_GRANULARITY_SHIFT  9
//! Number of medium block size classes
#define MEDIUM_CLASS_COUNT        61
//! Total number of small + medium size classes
#define SIZE_CLASS_COUNT          (SMALL_CLASS_COUNT + MEDIUM_CLASS_COUNT)
//! Number of large block size classes
#define LARGE_CLASS_COUNT         63
//! Maximum size of a medium block
#define MEDIUM_SIZE_LIMIT         (SMALL_SIZE_LIMIT + (MEDIUM_GRANULARITY * MEDIUM_CLASS_COUNT))
//! Maximum size of a large block
#define LARGE_SIZE_LIMIT          ((LARGE_CLASS_COUNT * _memory_span_size) - SPAN_HEADER_SIZE)
//! Size of a span header (must be a multiple of SMALL_GRANULARITY and a power of two)
#define SPAN_HEADER_SIZE          128
//! Number of spans in thread cache
#define MAX_THREAD_SPAN_CACHE     256
//! Number of spans to transfer between thread and global cache
#define THREAD_SPAN_CACHE_TRANSFER 64
//! Number of spans in thread cache for large spans (must be greater than LARGE_CLASS_COUNT / 2)
#define MAX_THREAD_SPAN_LARGE_CACHE 64
//! Number of spans to transfer between thread and global cache for large spans
#define THREAD_SPAN_LARGE_CACHE_TRANSFER 6

_Static_assert((SMALL_GRANULARITY & (SMALL_GRANULARITY - 1)) == 0, "Small granularity must be power of two");
_Static_assert((SPAN_HEADER_SIZE & (SPAN_HEADER_SIZE - 1)) == 0, "Span header size must be power of two");

#if ENABLE_VALIDATE_ARGS
//! Maximum allocation size to avoid integer overflow
#undef  MAX_ALLOC_SIZE
#define MAX_ALLOC_SIZE            (((size_t)-1) - _memory_span_size)
#endif

#define pointer_offset(ptr, ofs) (void*)((char*)(ptr) + (ptrdiff_t)(ofs))
#define pointer_diff(first, second) (ptrdiff_t)((const char*)(first) - (const char*)(second))

#define INVALID_POINTER ((void*)((uintptr_t)-1))

#define SIZE_CLASS_LARGE SIZE_CLASS_COUNT
#define SIZE_CLASS_HUGE ((uint32_t)-1)

////////////
///
/// Data types
///
//////

//! A memory heap, per thread
typedef struct heap_t heap_t;
//! Span of memory pages
typedef struct span_t span_t;
//! Span list
typedef struct span_list_t span_list_t;
//! Span active data
typedef struct span_active_t span_active_t;
//! Size class definition
typedef struct size_class_t size_class_t;
//! Global cache
typedef struct global_cache_t global_cache_t;

//! Flag indicating span is the first (master) span of a split superspan
#define SPAN_FLAG_MASTER 1U
//! Flag indicating span is a secondary (sub) span of a split superspan
#define SPAN_FLAG_SUBSPAN 2U
//! Flag indicating span has blocks with increased alignment
#define SPAN_FLAG_ALIGNED_BLOCKS 4U
//! Flag indicating an unmapped master span
#define SPAN_FLAG_UNMAPPED_MASTER 8U

#if ENABLE_ADAPTIVE_THREAD_CACHE || ENABLE_STATISTICS
struct span_use_t {
	//! Current number of spans used (actually used, not in cache)
	atomic32_t current;
	//! High water mark of spans used
	atomic32_t high;
#if ENABLE_STATISTICS
	//! Number of spans in deferred list
	atomic32_t spans_deferred;
	//! Number of spans transitioned to global cache
	atomic32_t spans_to_global;
	//! Number of spans transitioned from global cache
	atomic32_t spans_from_global;
	//! Number of spans transitioned to thread cache
	atomic32_t spans_to_cache;
	//! Number of spans transitioned from thread cache
	atomic32_t spans_from_cache;
	//! Number of spans transitioned to reserved state
	atomic32_t spans_to_reserved;
	//! Number of spans transitioned from reserved state
	atomic32_t spans_from_reserved;
	//! Number of raw memory map calls
	atomic32_t spans_map_calls;
#endif
};
typedef struct span_use_t span_use_t;
#endif

#if ENABLE_STATISTICS
struct size_class_use_t {
	//! Current number of allocations
	atomic32_t alloc_current;
	//! Peak number of allocations
	int32_t alloc_peak;
	//! Total number of allocations
	atomic32_t alloc_total;
	//! Total number of frees
	atomic32_t free_total;
	//! Number of spans in use
	atomic32_t spans_current;
	//! Number of spans transitioned to cache
	int32_t spans_peak;
	//! Number of spans transitioned to cache
	atomic32_t spans_to_cache;
	//! Number of spans transitioned from cache
	atomic32_t spans_from_cache;
	//! Number of spans transitioned from reserved state
	atomic32_t spans_from_reserved;
	//! Number of spans mapped
	atomic32_t spans_map_calls;
	int32_t unused;
};
typedef struct size_class_use_t size_class_use_t;
#endif

// A span can either represent a single span of memory pages with size declared by span_map_count configuration variable,
// or a set of spans in a continuous region, a super span. Any reference to the term "span" usually refers to both a single
// span or a super span. A super span can further be divided into multiple spans (or this, super spans), where the first
// (super)span is the master and subsequent (super)spans are subspans. The master span keeps track of how many subspans
// that are still alive and mapped in virtual memory, and once all subspans and master have been unmapped the entire
// superspan region is released and unmapped (on Windows for example, the entire superspan range has to be released
// in the same call to release the virtual memory range, but individual subranges can be decommitted individually
// to reduce physical memory use).
struct span_t {
	//! Free list
	void*       free_list;
	//! Total block count of size class
	uint32_t    block_count;
	//! Size class
	uint32_t    size_class;
	//! Index of last block initialized in free list
	uint32_t    free_list_limit;
	//! Number of used blocks remaining when in partial state
	uint32_t    used_count;
	//! Deferred free list
	atomicptr_t free_list_deferred;
	//! Size of deferred free list, or list of spans when part of a cache list
	uint32_t    list_size;
	//! Size of a block
	uint32_t    block_size;
	//! Flags and counters
	uint32_t    flags;
	//! Number of spans
	uint32_t    span_count;
	//! Total span counter for master spans
	uint32_t    total_spans;
	//! Offset from master span for subspans
	uint32_t    offset_from_master;
	//! Remaining span counter, for master spans
	atomic32_t  remaining_spans;
	//! Alignment offset
	uint32_t    align_offset;
	//! Owning heap
	heap_t*     heap;
	//! Next span
	span_t*     next;
	//! Previous span
	span_t*     prev;
};
_Static_assert(sizeof(span_t) <= SPAN_HEADER_SIZE, "span size mismatch");

struct span_cache_t {
	size_t       count;
	span_t*      span[MAX_THREAD_SPAN_CACHE];
};
typedef struct span_cache_t span_cache_t;

struct span_large_cache_t {
	size_t       count;
	span_t*      span[MAX_THREAD_SPAN_LARGE_CACHE];
};
typedef struct span_large_cache_t span_large_cache_t;

struct heap_size_class_t {
	//! Free list of active span
	void*        free_list;
	//! Double linked list of partially used spans with free blocks.
	//  Previous span pointer in head points to tail span of list.
	span_t*      partial_span;
	//! Early level cache of fully free spans
	span_t*      cache;
};
typedef struct heap_size_class_t heap_size_class_t;

// Control structure for a heap, either a thread heap or a first class heap if enabled
struct heap_t {
	//! Owning thread ID
	uintptr_t    owner_thread;
	//! Free lists for each size class
	heap_size_class_t size_class[SIZE_CLASS_COUNT];
#if ENABLE_THREAD_CACHE
	//! Arrays of fully freed spans, single span
	span_cache_t span_cache;
#endif
	//! List of deferred free spans (single linked list)
	atomicptr_t  span_free_deferred;
	//! Number of full spans
	size_t       full_span_count;
	//! Mapped but unused spans
	span_t*      span_reserve;
	//! Master span for mapped but unused spans
	span_t*      span_reserve_master;
	//! Number of mapped but unused spans
	uint32_t     spans_reserved;
	//! Child count
	atomic32_t   child_count;
	//! Next heap in id list
	heap_t*      next_heap;
	//! Next heap in orphan list
	heap_t*      next_orphan;
	//! Heap ID
	int32_t      id;
	//! Finalization state flag
	int          finalize;
	//! Master heap owning the memory pages
	heap_t*      master_heap;
#if ENABLE_THREAD_CACHE
	//! Arrays of fully freed spans, large spans with > 1 span count
	span_large_cache_t span_large_cache[LARGE_CLASS_COUNT - 1];
#endif
#if RPMALLOC_FIRST_CLASS_HEAPS
	//! Double linked list of fully utilized spans with free blocks for each size class.
	//  Previous span pointer in head points to tail span of list.
	span_t*      full_span[SIZE_CLASS_COUNT];
	//! Double linked list of large and huge spans allocated by this heap
	span_t*      large_huge_span;
#endif
#if ENABLE_ADAPTIVE_THREAD_CACHE || ENABLE_STATISTICS
	//! Current and high water mark of spans used per span count
	span_use_t   span_use[LARGE_CLASS_COUNT];
#endif
#if ENABLE_STATISTICS
	//! Allocation stats per size class
	size_class_use_t size_class_use[SIZE_CLASS_COUNT + 1];
	//! Number of bytes transitioned thread -> global
	atomic64_t   thread_to_global;
	//! Number of bytes transitioned global -> thread
	atomic64_t   global_to_thread;
#endif
};

// Size class for defining a block size bucket
struct size_class_t {
	//! Size of blocks in this class
	uint32_t block_size;
	//! Number of blocks in each chunk
	uint16_t block_count;
	//! Class index this class is merged with
	uint16_t class_idx;
};
_Static_assert(sizeof(size_class_t) == 8, "Size class size mismatch");

struct global_cache_t {
	//! Cache lock
	atomic32_t lock;
	//! Cache count
	uint32_t count;
	//! Cached spans
	span_t* span[GLOBAL_CACHE_MULTIPLIER * MAX_THREAD_SPAN_CACHE];
	//! Unlimited cache overflow
	span_t* overflow;
};

////////////
///
/// Global data
///
//////

//! Default span size (64KiB)
#define _memory_default_span_size (64 * 1024)
#define _memory_default_span_size_shift 16
#define _memory_default_span_mask (~((uintptr_t)(_memory_span_size - 1)))

//! Initialized flag
static int _rpmalloc_initialized;
//! Main thread ID
static uintptr_t _rpmalloc_main_thread_id;
//! Configuration
static rpmalloc_config_t _memory_config;
//! Memory page size
static size_t _memory_page_size;
//! Shift to divide by page size
static size_t _memory_page_size_shift;
//! Granularity at which memory pages are mapped by OS
static size_t _memory_map_granularity;
#if RPMALLOC_CONFIGURABLE
//! Size of a span of memory pages
static size_t _memory_span_size;
//! Shift to divide by span size
static size_t _memory_span_size_shift;
//! Mask to get to start of a memory span
static uintptr_t _memory_span_mask;
#else
//! Hardwired span size
#define _memory_span_size _memory_default_span_size
#define _memory_span_size_shift _memory_default_span_size_shift
#define _memory_span_mask _memory_default_span_mask
#endif
//! Number of spans to map in each map call
static size_t _memory_span_map_count;
//! Number of spans to release from thread cache to global cache (single spans)
static size_t _memory_span_release_count;
//! Number of spans to release from thread cache to global cache (large multiple spans)
static size_t _memory_span_release_count_large;
//! Global size classes
static size_class_t _memory_size_class[SIZE_CLASS_COUNT];
//! Run-time size limit of medium blocks
static size_t _memory_medium_size_limit;
//! Heap ID counter
static atomic32_t _memory_heap_id;
//! Huge page support
static int _memory_huge_pages;
#if ENABLE_GLOBAL_CACHE
//! Global span cache
static global_cache_t _memory_span_cache[LARGE_CLASS_COUNT];
#endif
//! Global reserved spans
static span_t* _memory_global_reserve;
//! Global reserved count
static size_t _memory_global_reserve_count;
//! Global reserved master
static span_t* _memory_global_reserve_master;
//! All heaps
static heap_t* _memory_heaps[HEAP_ARRAY_SIZE];
//! Used to restrict access to mapping memory for huge pages
static atomic32_t _memory_global_lock;
//! Orphaned heaps
static heap_t* _memory_orphan_heaps;
#if RPMALLOC_FIRST_CLASS_HEAPS
//! Orphaned heaps (first class heaps)
static heap_t* _memory_first_class_orphan_heaps;
#endif
#if ENABLE_STATISTICS
//! Allocations counter
static atomic64_t _allocation_counter;
//! Deallocations counter
static atomic64_t _deallocation_counter;
//! Active heap count
static atomic32_t _memory_active_heaps;
//! Number of currently mapped memory pages
static atomic32_t _mapped_pages;
//! Peak number of concurrently mapped memory pages
static int32_t _mapped_pages_peak;
//! Number of mapped master spans
static atomic32_t _master_spans;
//! Number of unmapped dangling master spans
static atomic32_t _unmapped_master_spans;
//! Number of currently unused spans
static atomic32_t _reserved_spans;
//! Running counter of total number of mapped memory pages since start
static atomic32_t _mapped_total;
//! Running counter of total number of unmapped memory pages since start
static atomic32_t _unmapped_total;
//! Number of currently mapped memory pages in OS calls
static atomic32_t _mapped_pages_os;
//! Number of currently allocated pages in huge allocations
static atomic32_t _huge_pages_current;
//! Peak number of currently allocated pages in huge allocations
static int32_t _huge_pages_peak;
#endif

////////////
///
/// Thread local heap and ID
///
//////

//! Current thread heap
#if (defined(__APPLE__) || defined(__HAIKU__)) && ENABLE_PRELOAD
static pthread_key_t _memory_thread_heap;
#else
#  ifdef _MSC_VER
#    define _Thread_local __declspec(thread)
#    define TLS_MODEL
#  else
#    ifndef __HAIKU__
#      define TLS_MODEL __attribute__((tls_model("initial-exec")))
#    else
#      define TLS_MODEL
#    endif
#    if !defined(__clang__) && defined(__GNUC__)
#      define _Thread_local __thread
#    endif
#  endif
static _Thread_local heap_t* _memory_thread_heap TLS_MODEL;
#endif

static inline heap_t*
get_thread_heap_raw(void) {
#if (defined(__APPLE__) || defined(__HAIKU__)) && ENABLE_PRELOAD
	return pthread_getspecific(_memory_thread_heap);
#else
	return _memory_thread_heap;
#endif
}

//! Get the current thread heap
static inline heap_t*
get_thread_heap(void) {
	heap_t* heap = get_thread_heap_raw();
#if ENABLE_PRELOAD
	if (EXPECTED(heap != 0))
		return heap;
	rpmalloc_initialize();
	return get_thread_heap_raw();
#else
	return heap;
#endif
}

//! Fast thread ID
static inline uintptr_t
get_thread_id(void) {
#if defined(_WIN32)
	return (uintptr_t)((void*)NtCurrentTeb());
#elif defined(__GNUC__) || defined(__clang__)
	uintptr_t tid;
#  if defined(__i386__)
	__asm__("movl %%gs:0, %0" : "=r" (tid) : : );
#  elif defined(__x86_64__)
#    if defined(__MACH__)
	__asm__("movq %%gs:0, %0" : "=r" (tid) : : );
#    else
	__asm__("movq %%fs:0, %0" : "=r" (tid) : : );
#    endif
#  elif defined(__arm__)
	__asm__ volatile ("mrc p15, 0, %0, c13, c0, 3" : "=r" (tid));
#  elif defined(__aarch64__)
#    if defined(__MACH__)
	// tpidr_el0 likely unused, always return 0 on iOS
	__asm__ volatile ("mrs %0, tpidrro_el0" : "=r" (tid));
#    else
	__asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tid));
#    endif
#  else
	tid = (uintptr_t)((void*)get_thread_heap_raw());
#  endif
	return tid;
#else
	return (uintptr_t)((void*)get_thread_heap_raw());
#endif
}

//! Set the current thread heap
static void
set_thread_heap(heap_t* heap) {
#if (defined(__APPLE__) || defined(__HAIKU__)) && ENABLE_PRELOAD
	pthread_setspecific(_memory_thread_heap, heap);
#else
	_memory_thread_heap = heap;
#endif
	if (heap)
		heap->owner_thread = get_thread_id();
}

//! Set main thread ID
extern void
rpmalloc_set_main_thread(void);

void
rpmalloc_set_main_thread(void) {
	_rpmalloc_main_thread_id = get_thread_id();
}

static void
_rpmalloc_spin(void) {
#if defined(_MSC_VER)
	_mm_pause();
#elif defined(__x86_64__) || defined(__i386__)
	__asm__ volatile("pause" ::: "memory");
#elif defined(__aarch64__) || (defined(__arm__) && __ARM_ARCH >= 7)
	__asm__ volatile("yield" ::: "memory");
#elif defined(__powerpc__) || defined(__powerpc64__)
        // No idea if ever been compiled in such archs but ... as precaution
	__asm__ volatile("or 27,27,27");
#elif defined(__sparc__)
	__asm__ volatile("rd %ccr, %g0 \n\trd %ccr, %g0 \n\trd %ccr, %g0");
#else
	struct timespec ts = {0};
	nanosleep(&ts, 0);
#endif
}

#if defined(_WIN32) && (!defined(BUILD_DYNAMIC_LINK) || !BUILD_DYNAMIC_LINK)
static void NTAPI
_rpmalloc_thread_destructor(void* value) {
#if ENABLE_OVERRIDE
	// If this is called on main thread it means rpmalloc_finalize
	// has not been called and shutdown is forced (through _exit) or unclean
	if (get_thread_id() == _rpmalloc_main_thread_id)
		return;
#endif
	if (value)
		rpmalloc_thread_finalize(1);
}
#endif


////////////
///
/// Low level memory map/unmap
///
//////

//! Map more virtual memory
//  size is number of bytes to map
//  offset receives the offset in bytes from start of mapped region
//  returns address to start of mapped region to use
static void*
_rpmalloc_mmap(size_t size, size_t* offset) {
	assert(!(size % _memory_page_size));
	assert(size >= _memory_page_size);
	_rpmalloc_stat_add_peak(&_mapped_pages, (size >> _memory_page_size_shift), _mapped_pages_peak);
	_rpmalloc_stat_add(&_mapped_total, (size >> _memory_page_size_shift));
	return _memory_config.memory_map(size, offset);
}

//! Unmap virtual memory
//  address is the memory address to unmap, as returned from _memory_map
//  size is the number of bytes to unmap, which might be less than full region for a partial unmap
//  offset is the offset in bytes to the actual mapped region, as set by _memory_map
//  release is set to 0 for partial unmap, or size of entire range for a full unmap
static void
_rpmalloc_unmap(void* address, size_t size, size_t offset, size_t release) {
	assert(!release || (release >= size));
	assert(!release || (release >= _memory_page_size));
	if (release) {
		assert(!(release % _memory_page_size));
		_rpmalloc_stat_sub(&_mapped_pages, (release >> _memory_page_size_shift));
		_rpmalloc_stat_add(&_unmapped_total, (release >> _memory_page_size_shift));
	}
	_memory_config.memory_unmap(address, size, offset, release);
}

//! Default implementation to map new pages to virtual memory
static void*
_rpmalloc_mmap_os(size_t size, size_t* offset) {
	//Either size is a heap (a single page) or a (multiple) span - we only need to align spans, and only if larger than map granularity
	size_t padding = ((size >= _memory_span_size) && (_memory_span_size > _memory_map_granularity)) ? _memory_span_size : 0;
	assert(size >= _memory_page_size);
#if PLATFORM_WINDOWS
	//Ok to MEM_COMMIT - according to MSDN, "actual physical pages are not allocated unless/until the virtual addresses are actually accessed"
	void* ptr = VirtualAlloc(0, size + padding, (_memory_huge_pages ? MEM_LARGE_PAGES : 0) | MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
	if (!ptr) {
		assert(ptr && "Failed to map virtual memory block");
		return 0;
	}
#else
	int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_UNINITIALIZED;
#  if defined(__APPLE__) && !TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR
	int fd = (int)VM_MAKE_TAG(240U);
	if (_memory_huge_pages)
		fd |= VM_FLAGS_SUPERPAGE_SIZE_2MB;
	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, flags, fd, 0);
#  elif defined(MAP_HUGETLB)
	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE | PROT_MAX(PROT_READ | PROT_WRITE), (_memory_huge_pages ? MAP_HUGETLB : 0) | flags, -1, 0);
#  elif defined(MAP_ALIGNED)
	const size_t align = (sizeof(size_t) * 8) - (size_t)(__builtin_clzl(size - 1));
	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, (_memory_huge_pages ? MAP_ALIGNED(align) : 0) | flags, -1, 0);
#  elif defined(MAP_ALIGN)
	caddr_t base = (_memory_huge_pages ? (caddr_t)(4 << 20) : 0);
	void* ptr = mmap(base, size + padding, PROT_READ | PROT_WRITE, (_memory_huge_pages ? MAP_ALIGN : 0) | flags, -1, 0);
#  else
	void* ptr = mmap(0, size + padding, PROT_READ | PROT_WRITE, flags, -1, 0);
#  endif
	if ((ptr == MAP_FAILED) || !ptr) {
		if (errno != ENOMEM)
			assert("Failed to map virtual memory block" == 0);
		return 0;
	}
#endif
	_rpmalloc_stat_add(&_mapped_pages_os, (int32_t)((size + padding) >> _memory_page_size_shift));
	if (padding) {
		size_t final_padding = padding - ((uintptr_t)ptr & ~_memory_span_mask);
		assert(final_padding <= _memory_span_size);
		assert(final_padding <= padding);
		assert(!(final_padding % 8));
		ptr = pointer_offset(ptr, final_padding);
		*offset = final_padding >> 3;
	}
	assert((size < _memory_span_size) || !((uintptr_t)ptr & ~_memory_span_mask));
	return ptr;
}

//! Default implementation to unmap pages from virtual memory
static void
_rpmalloc_unmap_os(void* address, size_t size, size_t offset, size_t release) {
	assert(release || (offset == 0));
	assert(!release || (release >= _memory_page_size));
	assert(size >= _memory_page_size);
	if (release && offset) {
		offset <<= 3;
		address = pointer_offset(address, -(int32_t)offset);
		if ((release >= _memory_span_size) && (_memory_span_size > _memory_map_granularity)) {
			//Padding is always one span size
			release += _memory_span_size;
		}
	}
#if !DISABLE_UNMAP
#if PLATFORM_WINDOWS
	if (!VirtualFree(address, release ? 0 : size, release ? MEM_RELEASE : MEM_DECOMMIT)) {
		assert(address && "Failed to unmap virtual memory block");
	}
#else
	if (release) {
		if (munmap(address, release)) {
			assert("Failed to unmap virtual memory block" == 0);
		}
	} else {
#if defined(MADV_FREE_REUSABLE)
		int ret;
		while ((ret = madvise(address, size, MADV_FREE_REUSABLE)) == -1 && errno == EAGAIN);
		if (ret == -1 && errno != 0)
#elif defined(MADV_FREE)
		if (madvise(address, size, MADV_FREE))
#endif
#if defined(MADV_DONTNEED)
		if (madvise(address, size, MADV_DONTNEED)) {
#else
		if (posix_madvise(address, size, POSIX_MADV_DONTNEED)) {
#endif
			assert("Failed to madvise virtual memory block as free" == 0);
		}
	}
#endif
#endif
	if (release)
		_rpmalloc_stat_sub(&_mapped_pages_os, release >> _memory_page_size_shift);
}

static void
_rpmalloc_span_mark_as_subspan_unless_master(span_t* master, span_t* subspan, size_t span_count);

//! Use global reserved spans to fulfill a memory map request (reserve size must be checked by caller)
static span_t*
_rpmalloc_global_get_reserved_spans(size_t span_count) {
	span_t* span = _memory_global_reserve;
	_rpmalloc_span_mark_as_subspan_unless_master(_memory_global_reserve_master, span, span_count);
	_memory_global_reserve_count -= span_count;
	if (_memory_global_reserve_count)
		_memory_global_reserve = (span_t*)pointer_offset(span, span_count << _memory_span_size_shift);
	else
		_memory_global_reserve = 0;
	return span;
}

//! Store the given spans as global reserve (must only be called from within new heap allocation, not thread safe)
static void
_rpmalloc_global_set_reserved_spans(span_t* master, span_t* reserve, size_t reserve_span_count) {
	_memory_global_reserve_master = master;
	_memory_global_reserve_count = reserve_span_count;
	_memory_global_reserve = reserve;
}


////////////
///
/// Span linked list management
///
//////

//! Add a span to double linked list at the head
static void
_rpmalloc_span_double_link_list_add(span_t** head, span_t* span) {
	if (*head) {
		span->next = *head;
		(*head)->prev = span;
	} else {
		span->next = 0;
	}
	*head = span;
}

//! Pop head span from double linked list
static void
_rpmalloc_span_double_link_list_pop_head(span_t** head, span_t* span) {
	assert(*head == span);
	span = *head;
	*head = span->next;
}

//! Remove a span from double linked list
static void
_rpmalloc_span_double_link_list_remove(span_t** head, span_t* span) {
	assert(*head);
	if (*head == span) {
		*head = span->next;
	} else {
		span_t* next_span = span->next;
		span_t* prev_span = span->prev;
		prev_span->next = next_span;
		if (EXPECTED(next_span != 0)) {
			next_span->prev = prev_span;
		}
	}
}


////////////
///
/// Span control
///
//////

static void
_rpmalloc_heap_cache_insert(heap_t* heap, span_t* span);

static void
_rpmalloc_heap_finalize(heap_t* heap);

static void
_rpmalloc_heap_set_reserved_spans(heap_t* heap, span_t* master, span_t* reserve, size_t reserve_span_count);

//! Declare the span to be a subspan and store distance from master span and span count
static void
_rpmalloc_span_mark_as_subspan_unless_master(span_t* master, span_t* subspan, size_t span_count) {
	assert((subspan != master) || (subspan->flags & SPAN_FLAG_MASTER));
	if (subspan != master) {
		subspan->flags = SPAN_FLAG_SUBSPAN;
		subspan->offset_from_master = (uint32_t)((uintptr_t)pointer_diff(subspan, master) >> _memory_span_size_shift);
		subspan->align_offset = 0;
	}
	subspan->span_count = (uint32_t)span_count;
}

//! Use reserved spans to fulfill a memory map request (reserve size must be checked by caller)
static span_t*
_rpmalloc_span_map_from_reserve(heap_t* heap, size_t span_count) {
	//Update the heap span reserve
	span_t* span = heap->span_reserve;
	heap->span_reserve = (span_t*)pointer_offset(span, span_count * _memory_span_size);
	heap->spans_reserved -= (uint32_t)span_count;

	_rpmalloc_span_mark_as_subspan_unless_master(heap->span_reserve_master, span, span_count);
	if (span_count <= LARGE_CLASS_COUNT)
		_rpmalloc_stat_inc(&heap->span_use[span_count - 1].spans_from_reserved);

	return span;
}

//! Get the aligned number of spans to map in based on wanted count, configured mapping granularity and the page size
static size_t
_rpmalloc_span_align_count(size_t span_count) {
	size_t request_count = (span_count > _memory_span_map_count) ? span_count : _memory_span_map_count;
	if ((_memory_page_size > _memory_span_size) && ((request_count * _memory_span_size) % _memory_page_size))
		request_count += _memory_span_map_count - (request_count % _memory_span_map_count);
	return request_count;
}

//! Setup a newly mapped span
static void
_rpmalloc_span_initialize(span_t* span, size_t total_span_count, size_t span_count, size_t align_offset) {
	span->total_spans = (uint32_t)total_span_count;
	span->span_count = (uint32_t)span_count;
	span->align_offset = (uint32_t)align_offset;
	span->flags = SPAN_FLAG_MASTER;
	atomic_store32(&span->remaining_spans, (int32_t)total_span_count);
}

static void
_rpmalloc_span_unmap(span_t* span);

//! Map an aligned set of spans, taking configured mapping granularity and the page size into account
static span_t*
_rpmalloc_span_map_aligned_count(heap_t* heap, size_t span_count) {
	//If we already have some, but not enough, reserved spans, release those to heap cache and map a new
	//full set of spans. Otherwise we would waste memory if page size > span size (huge pages)
	size_t aligned_span_count = _rpmalloc_span_align_count(span_count);
	size_t align_offset = 0;
	span_t* span = (span_t*)_rpmalloc_mmap(aligned_span_count * _memory_span_size, &align_offset);
	if (!span)
		return 0;
	_rpmalloc_span_initialize(span, aligned_span_count, span_count, align_offset);
	_rpmalloc_stat_add(&_reserved_spans, aligned_span_count);
	_rpmalloc_stat_inc(&_master_spans);
	if (span_count <= LARGE_CLASS_COUNT)
		_rpmalloc_stat_inc(&heap->span_use[span_count - 1].spans_map_calls);
	if (aligned_span_count > span_count) {
		span_t* reserved_spans = (span_t*)pointer_offset(span, span_count * _memory_span_size);
		size_t reserved_count = aligned_span_count - span_count;
		if (heap->spans_reserved) {
			_rpmalloc_span_mark_as_subspan_unless_master(heap->span_reserve_master, heap->span_reserve, heap->spans_reserved);
			_rpmalloc_heap_cache_insert(heap, heap->span_reserve);
		}
		if (reserved_count > DEFAULT_SPAN_MAP_COUNT) {
			// If huge pages, make sure only one thread maps more memory to avoid bloat
			while (!atomic_cas32_acquire(&_memory_global_lock, 1, 0))
				_rpmalloc_spin();
			size_t remain_count = reserved_count - DEFAULT_SPAN_MAP_COUNT;
			reserved_count = DEFAULT_SPAN_MAP_COUNT;
			span_t* remain_span = (span_t*)pointer_offset(reserved_spans, reserved_count * _memory_span_size);
			if (_memory_global_reserve) {
				_rpmalloc_span_mark_as_subspan_unless_master(_memory_global_reserve_master, _memory_global_reserve, _memory_global_reserve_count);
				_rpmalloc_span_unmap(_memory_global_reserve);
			}
			_rpmalloc_global_set_reserved_spans(span, remain_span, remain_count);
			atomic_store32_release(&_memory_global_lock, 0);
		}
		_rpmalloc_heap_set_reserved_spans(heap, span, reserved_spans, reserved_count);
	}
	return span;
}

//! Map in memory pages for the given number of spans (or use previously reserved pages)
static span_t*
_rpmalloc_span_map(heap_t* heap, size_t span_count) {
	if (span_count <= heap->spans_reserved)
		return _rpmalloc_span_map_from_reserve(heap, span_count);
	span_t* span = 0;
	if (_memory_page_size > _memory_span_size) {
		// If huge pages, make sure only one thread maps more memory to avoid bloat
		while (!atomic_cas32_acquire(&_memory_global_lock, 1, 0))
			_rpmalloc_spin();
		if (_memory_global_reserve_count >= span_count) {
			size_t reserve_count = (!heap->spans_reserved ? DEFAULT_SPAN_MAP_COUNT : span_count);
			if (_memory_global_reserve_count < reserve_count)
				reserve_count = _memory_global_reserve_count;
			span = _rpmalloc_global_get_reserved_spans(reserve_count);
			if (span) {
				if (reserve_count > span_count) {
					span_t* reserved_span = (span_t*)pointer_offset(span, span_count << _memory_span_size_shift);
					_rpmalloc_heap_set_reserved_spans(heap, _memory_global_reserve_master, reserved_span, reserve_count - span_count);
				}
				// Already marked as subspan in _rpmalloc_global_get_reserved_spans
				span->span_count = (uint32_t)span_count;
			}
		}
	}
	if (!span)
		span = _rpmalloc_span_map_aligned_count(heap, span_count);
	if (_memory_page_size > _memory_span_size)
		atomic_store32_release(&_memory_global_lock, 0);
	return span;
}

//! Unmap memory pages for the given number of spans (or mark as unused if no partial unmappings)
static void
_rpmalloc_span_unmap(span_t* span) {
	assert((span->flags & SPAN_FLAG_MASTER) || (span->flags & SPAN_FLAG_SUBSPAN));
	assert(!(span->flags & SPAN_FLAG_MASTER) || !(span->flags & SPAN_FLAG_SUBSPAN));

	int is_master = !!(span->flags & SPAN_FLAG_MASTER);
	span_t* master = is_master ? span : ((span_t*)pointer_offset(span, -(intptr_t)((uintptr_t)span->offset_from_master * _memory_span_size)));
	assert(is_master || (span->flags & SPAN_FLAG_SUBSPAN));
	assert(master->flags & SPAN_FLAG_MASTER);

	size_t span_count = span->span_count;
	if (!is_master) {
		//Directly unmap subspans (unless huge pages, in which case we defer and unmap entire page range with master)
		assert(span->align_offset == 0);
		if (_memory_span_size >= _memory_page_size) {
			_rpmalloc_unmap(span, span_count * _memory_span_size, 0, 0);
			_rpmalloc_stat_sub(&_reserved_spans, span_count);
		}
	} else {
		//Special double flag to denote an unmapped master
		//It must be kept in memory since span header must be used
		span->flags |= SPAN_FLAG_MASTER | SPAN_FLAG_SUBSPAN | SPAN_FLAG_UNMAPPED_MASTER;
		_rpmalloc_stat_add(&_unmapped_master_spans, 1);
	}

	if (atomic_add32(&master->remaining_spans, -(int32_t)span_count) <= 0) {
		//Everything unmapped, unmap the master span with release flag to unmap the entire range of the super span
		assert(!!(master->flags & SPAN_FLAG_MASTER) && !!(master->flags & SPAN_FLAG_SUBSPAN));
		size_t unmap_count = master->span_count;
		if (_memory_span_size < _memory_page_size)
			unmap_count = master->total_spans;
		_rpmalloc_stat_sub(&_reserved_spans, unmap_count);
		_rpmalloc_stat_sub(&_master_spans, 1);
		_rpmalloc_stat_sub(&_unmapped_master_spans, 1);
		_rpmalloc_unmap(master, unmap_count * _memory_span_size, master->align_offset, (size_t)master->total_spans * _memory_span_size);
	}
}

//! Move the span (used for small or medium allocations) to the heap thread cache
static void
_rpmalloc_span_release_to_cache(heap_t* heap, span_t* span) {
	assert(heap == span->heap);
	assert(span->size_class < SIZE_CLASS_COUNT);
#if ENABLE_ADAPTIVE_THREAD_CACHE || ENABLE_STATISTICS
	atomic_decr32(&heap->span_use[0].current);
#endif
	_rpmalloc_stat_dec(&heap->size_class_use[span->size_class].spans_current);
	if (!heap->finalize) {
		_rpmalloc_stat_inc(&heap->span_use[0].spans_to_cache);
		_rpmalloc_stat_inc(&heap->size_class_use[span->size_class].spans_to_cache);
		if (heap->size_class[span->size_class].cache)
			_rpmalloc_heap_cache_insert(heap, heap->size_class[span->size_class].cache);
		heap->size_class[span->size_class].cache = span;
	} else {
		_rpmalloc_span_unmap(span);
	}
}

//! Initialize a (partial) free list up to next system memory page, while reserving the first block
//! as allocated, returning number of blocks in list
static uint32_t
free_list_partial_init(void** list, void** first_block, void* page_start, void* block_start, uint32_t block_count, uint32_t block_size) {
	assert(block_count);
	*first_block = block_start;
	if (block_count > 1) {
		void* free_block = pointer_offset(block_start, block_size);
		void* block_end = pointer_offset(block_start, (size_t)block_size * block_count);
		//If block size is less than half a memory page, bound init to next memory page boundary
		if (block_size < (_memory_page_size >> 1)) {
			void* page_end = pointer_offset(page_start, _memory_page_size);
			if (page_end < block_end)
				block_end = page_end;
		}
		*list = free_block;
		block_count = 2;
		void* next_block = pointer_offset(free_block, block_size);
		while (next_block < block_end) {
			*((void**)free_block) = next_block;
			free_block = next_block;
			++block_count;
			next_block = pointer_offset(next_block, block_size);
		}
		*((void**)free_block) = 0;
	} else {
		*list = 0;
	}
	return block_count;
}

//! Initialize an unused span (from cache or mapped) to be new active span, putting the initial free list in heap class free list
static void*
_rpmalloc_span_initialize_new(heap_t* heap, span_t* span, uint32_t class_idx) {
	assert(span->span_count == 1);
	size_class_t* size_class = _memory_size_class + class_idx;
	span->size_class = class_idx;
	span->heap = heap;
	span->flags &= ~SPAN_FLAG_ALIGNED_BLOCKS;
	span->block_size = size_class->block_size;
	span->block_count = size_class->block_count;
	span->free_list = 0;
	span->list_size = 0;
	atomic_store_ptr_release(&span->free_list_deferred, 0);

	//Setup free list. Only initialize one system page worth of free blocks in list
	void* block;
	span->free_list_limit = free_list_partial_init(&heap->size_class[class_idx].free_list, &block, 
		span, pointer_offset(span, SPAN_HEADER_SIZE), size_class->block_count, size_class->block_size);
	//Link span as partial if there remains blocks to be initialized as free list, or full if fully initialized
	if (span->free_list_limit < span->block_count) {
		_rpmalloc_span_double_link_list_add(&heap->size_class[class_idx].partial_span, span);
		span->used_count = span->free_list_limit;
	} else {
#if RPMALLOC_FIRST_CLASS_HEAPS
		_rpmalloc_span_double_link_list_add(&heap->full_span[class_idx], span);
#endif
		++heap->full_span_count;
		span->used_count = span->block_count;
	}
	return block;
}

static void
_rpmalloc_span_extract_free_list_deferred(span_t* span) {
	// We need acquire semantics on the CAS operation since we are interested in the list size
	// Refer to _rpmalloc_deallocate_defer_small_or_medium for further comments on this dependency
	do {
		span->free_list = atomic_exchange_ptr_acquire(&span->free_list_deferred, INVALID_POINTER);
	} while (span->free_list == INVALID_POINTER);
	span->used_count -= span->list_size;
	span->list_size = 0;
	atomic_store_ptr_release(&span->free_list_deferred, 0);
}

static int
_rpmalloc_span_is_fully_utilized(span_t* span) {
	assert(span->free_list_limit <= span->block_count);
	return !span->free_list && (span->free_list_limit >= span->block_count);
}

static int
_rpmalloc_span_finalize(heap_t* heap, size_t iclass, span_t* span, span_t** list_head) {
	void* free_list = heap->size_class[iclass].free_list;
	span_t* class_span = (span_t*)((uintptr_t)free_list & _memory_span_mask);
	if (span == class_span) {
		// Adopt the heap class free list back into the span free list
		void* block = span->free_list;
		void* last_block = 0;
		while (block) {
			last_block = block;
			block = *((void**)block);
		}
		uint32_t free_count = 0;
		block = free_list;
		while (block) {
			++free_count;
			block = *((void**)block);
		}
		if (last_block) {
			*((void**)last_block) = free_list;
		} else {
			span->free_list = free_list;
		}
		heap->size_class[iclass].free_list = 0;
		span->used_count -= free_count;
	}
	//If this assert triggers you have memory leaks
	assert(span->list_size == span->used_count);
	if (span->list_size == span->used_count) {
		_rpmalloc_stat_dec(&heap->span_use[0].current);
		_rpmalloc_stat_dec(&heap->size_class_use[iclass].spans_current);
		// This function only used for spans in double linked lists
		if (list_head)
			_rpmalloc_span_double_link_list_remove(list_head, span);
		_rpmalloc_span_unmap(span);
		return 1;
	}
	return 0;
}


////////////
///
/// Global cache
///
//////

#if ENABLE_GLOBAL_CACHE

//! Finalize a global cache
static void
_rpmalloc_global_cache_finalize(global_cache_t* cache) {
	while (!atomic_cas32_acquire(&cache->lock, 1, 0))
		_rpmalloc_spin();

	for (size_t ispan = 0; ispan < cache->count; ++ispan)
		_rpmalloc_span_unmap(cache->span[ispan]);
	cache->count = 0;

	while (cache->overflow) {
		span_t* span = cache->overflow;
		cache->overflow = span->next;
		_rpmalloc_span_unmap(span);
	}

	atomic_store32_release(&cache->lock, 0);
}

static void
_rpmalloc_global_cache_insert_spans(span_t** span, size_t span_count, size_t count) {
	const size_t cache_limit = (span_count == 1) ? 
		GLOBAL_CACHE_MULTIPLIER * MAX_THREAD_SPAN_CACHE :
		GLOBAL_CACHE_MULTIPLIER * (MAX_THREAD_SPAN_LARGE_CACHE - (span_count >> 1));

	global_cache_t* cache = &_memory_span_cache[span_count - 1];

	size_t insert_count = count;
	while (!atomic_cas32_acquire(&cache->lock, 1, 0))
		_rpmalloc_spin();

	if ((cache->count + insert_count) > cache_limit)
		insert_count = cache_limit - cache->count;

	memcpy(cache->span + cache->count, span, sizeof(span_t*) * insert_count);
	cache->count += (uint32_t)insert_count;

#if ENABLE_UNLIMITED_CACHE
	while (insert_count < count) {
#else
	// Enable unlimited cache if huge pages, or we will leak since it is unlikely that an entire huge page
	// will be unmapped, and we're unable to partially decommit a huge page
	while ((_memory_page_size > _memory_span_size) && (insert_count < count)) {
#endif		
		span_t* current_span = span[insert_count++];
		current_span->next = cache->overflow;
		cache->overflow = current_span;
	}
	atomic_store32_release(&cache->lock, 0);

	span_t* keep = 0;
	for (size_t ispan = insert_count; ispan < count; ++ispan) {
		span_t* current_span = span[ispan];
		// Keep master spans that has remaining subspans to avoid dangling them
		if ((current_span->flags & SPAN_FLAG_MASTER) &&
		    (atomic_load32(&current_span->remaining_spans) > (int32_t)current_span->span_count)) {
			current_span->next = keep;
			keep = current_span;
		} else {
			_rpmalloc_span_unmap(current_span);
		}
	}

	if (keep) {
		while (!atomic_cas32_acquire(&cache->lock, 1, 0))
			_rpmalloc_spin();

		size_t islot = 0;
		while (keep) {
			for (; islot < cache->count; ++islot) {
				span_t* current_span = cache->span[islot];
				if (!(current_span->flags & SPAN_FLAG_MASTER) || ((current_span->flags & SPAN_FLAG_MASTER) &&
				    (atomic_load32(&current_span->remaining_spans) <= (int32_t)current_span->span_count))) {
					_rpmalloc_span_unmap(current_span);
					cache->span[islot] = keep;
					break;
				}
			}
			if (islot == cache->count)
				break;
			keep = keep->next;
		}

		while (keep) {
			span_t* next_span = keep->next;
			keep->next = cache->overflow;
			cache->overflow = keep;
			keep = next_span;
		}

		atomic_store32_release(&cache->lock, 0);
	}
}

static size_t
_rpmalloc_global_cache_extract_spans(span_t** span, size_t span_count, size_t count) {
	global_cache_t* cache = &_memory_span_cache[span_count - 1];

	size_t extract_count = 0;
	while (!atomic_cas32_acquire(&cache->lock, 1, 0))
		_rpmalloc_spin();

	size_t want = count - extract_count;
	if (want > cache->count)
		want = cache->count;

	memcpy(span + extract_count, cache->span + (cache->count - want), sizeof(span_t*) * want);
	cache->count -= (uint32_t)want;
	extract_count += want;

	while ((extract_count < count) && cache->overflow) {
		span_t* current_span = cache->overflow;
		span[extract_count++] = current_span;
		cache->overflow = current_span->next;
	}

	atomic_store32_release(&cache->lock, 0);

	return extract_count;
}

#endif

////////////
///
/// Heap control
///
//////

static void _rpmalloc_deallocate_huge(span_t*);

//! Store the given spans as reserve in the given heap
static void
_rpmalloc_heap_set_reserved_spans(heap_t* heap, span_t* master, span_t* reserve, size_t reserve_span_count) {
	heap->span_reserve_master = master;
	heap->span_reserve = reserve;
	heap->spans_reserved = (uint32_t)reserve_span_count;
}

//! Adopt the deferred span cache list, optionally extracting the first single span for immediate re-use
static void
_rpmalloc_heap_cache_adopt_deferred(heap_t* heap, span_t** single_span) {
	span_t* span = (span_t*)((void*)atomic_exchange_ptr_acquire(&heap->span_free_deferred, 0));
	while (span) {
		span_t* next_span = (span_t*)span->free_list;
		assert(span->heap == heap);
		if (EXPECTED(span->size_class < SIZE_CLASS_COUNT)) {
			assert(heap->full_span_count);
			--heap->full_span_count;
			_rpmalloc_stat_dec(&heap->span_use[0].spans_deferred);
#if RPMALLOC_FIRST_CLASS_HEAPS
			_rpmalloc_span_double_link_list_remove(&heap->full_span[span->size_class], span);
#endif
			_rpmalloc_stat_dec(&heap->span_use[0].current);
			_rpmalloc_stat_dec(&heap->size_class_use[span->size_class].spans_current);
			if (single_span && !*single_span)
				*single_span = span;
			else
				_rpmalloc_heap_cache_insert(heap, span);
		} else {
			if (span->size_class == SIZE_CLASS_HUGE) {
				_rpmalloc_deallocate_huge(span);
			} else {
				assert(span->size_class == SIZE_CLASS_LARGE);
				assert(heap->full_span_count);
				--heap->full_span_count;
#if RPMALLOC_FIRST_CLASS_HEAPS
				_rpmalloc_span_double_link_list_remove(&heap->large_huge_span, span);
#endif
				uint32_t idx = span->span_count - 1;
				_rpmalloc_stat_dec(&heap->span_use[idx].spans_deferred);
				_rpmalloc_stat_dec(&heap->span_use[idx].current);
				if (!idx && single_span && !*single_span)
					*single_span = span;
				else
					_rpmalloc_heap_cache_insert(heap, span);
			}
		}
		span = next_span;
	}
}

static void
_rpmalloc_heap_unmap(heap_t* heap) {
	if (!heap->master_heap) {
		if ((heap->finalize > 1) && !atomic_load32(&heap->child_count)) {
			span_t* span = (span_t*)((uintptr_t)heap & _memory_span_mask);
			_rpmalloc_span_unmap(span);
		}
	} else {
		if (atomic_decr32(&heap->master_heap->child_count) == 0) {
			_rpmalloc_heap_unmap(heap->master_heap);
		}
	}
}

static void
_rpmalloc_heap_global_finalize(heap_t* heap) {
	if (heap->finalize++ > 1) {
		--heap->finalize;
		return;
	}

	_rpmalloc_heap_finalize(heap);

#if ENABLE_THREAD_CACHE
	for (size_t iclass = 0; iclass < LARGE_CLASS_COUNT; ++iclass) {
		span_cache_t* span_cache;
		if (!iclass)
			span_cache = &heap->span_cache;
		else
			span_cache = (span_cache_t*)(heap->span_large_cache + (iclass - 1));
		for (size_t ispan = 0; ispan < span_cache->count; ++ispan)
			_rpmalloc_span_unmap(span_cache->span[ispan]);
		span_cache->count = 0;
	}
#endif

	if (heap->full_span_count) {
		--heap->finalize;
		return;
	}

	for (size_t iclass = 0; iclass < SIZE_CLASS_COUNT; ++iclass) {
		if (heap->size_class[iclass].free_list || heap->size_class[iclass].partial_span) {
			--heap->finalize;
			return;
		}
	}
	//Heap is now completely free, unmap and remove from heap list
	size_t list_idx = (size_t)heap->id % HEAP_ARRAY_SIZE;
	heap_t* list_heap = _memory_heaps[list_idx];
	if (list_heap == heap) {
		_memory_heaps[list_idx] = heap->next_heap;
	} else {
		while (list_heap->next_heap != heap)
			list_heap = list_heap->next_heap;
		list_heap->next_heap = heap->next_heap;
	}

	_rpmalloc_heap_unmap(heap);
}

//! Insert a single span into thread heap cache, releasing to global cache if overflow
static void
_rpmalloc_heap_cache_insert(heap_t* heap, span_t* span) {
	if (UNEXPECTED(heap->finalize != 0)) {
		_rpmalloc_span_unmap(span);
		_rpmalloc_heap_global_finalize(heap);
		return;
	}
#if ENABLE_THREAD_CACHE
	size_t span_count = span->span_count;
	_rpmalloc_stat_inc(&heap->span_use[span_count - 1].spans_to_cache);
	if (span_count == 1) {
		span_cache_t* span_cache = &heap->span_cache;
		span_cache->span[span_cache->count++] = span;
		if (span_cache->count == MAX_THREAD_SPAN_CACHE) {
			const size_t remain_count = MAX_THREAD_SPAN_CACHE - THREAD_SPAN_CACHE_TRANSFER;
#if ENABLE_GLOBAL_CACHE
			_rpmalloc_stat_add64(&heap->thread_to_global, THREAD_SPAN_CACHE_TRANSFER * _memory_span_size);
			_rpmalloc_stat_add(&heap->span_use[span_count - 1].spans_to_global, THREAD_SPAN_CACHE_TRANSFER);
			_rpmalloc_global_cache_insert_spans(span_cache->span + remain_count, span_count, THREAD_SPAN_CACHE_TRANSFER);
#else
			for (size_t ispan = 0; ispan < THREAD_SPAN_CACHE_TRANSFER; ++ispan)
				_rpmalloc_span_unmap(span_cache->span[remain_count + ispan]);
#endif
			span_cache->count = remain_count;
		}
	} else {
		size_t cache_idx = span_count - 2;
		span_large_cache_t* span_cache = heap->span_large_cache + cache_idx;
		span_cache->span[span_cache->count++] = span;
		const size_t cache_limit = (MAX_THREAD_SPAN_LARGE_CACHE - (span_count >> 1));
		if (span_cache->count == cache_limit) {
			const size_t transfer_limit = 2 + (cache_limit >> 2);
			const size_t transfer_count = (THREAD_SPAN_LARGE_CACHE_TRANSFER <= transfer_limit ? THREAD_SPAN_LARGE_CACHE_TRANSFER : transfer_limit);
			const size_t remain_count = cache_limit - transfer_count;
#if ENABLE_GLOBAL_CACHE
			_rpmalloc_stat_add64(&heap->thread_to_global, transfer_count * span_count * _memory_span_size);
			_rpmalloc_stat_add(&heap->span_use[span_count - 1].spans_to_global, transfer_count);
			_rpmalloc_global_cache_insert_spans(span_cache->span + remain_count, span_count, transfer_count);
#else
			for (size_t ispan = 0; ispan < transfer_count; ++ispan)
				_rpmalloc_span_unmap(span_cache->span[remain_count + ispan]);
#endif
			span_cache->count = remain_count;
		}
	}
#else
	(void)sizeof(heap);
	_rpmalloc_span_unmap(span);
#endif
}

//! Extract the given number of spans from the different cache levels
static span_t*
_rpmalloc_heap_thread_cache_extract(heap_t* heap, size_t span_count) {
	span_t* span = 0;
#if ENABLE_THREAD_CACHE
	span_cache_t* span_cache;
	if (span_count == 1)
		span_cache = &heap->span_cache;
	else
		span_cache = (span_cache_t*)(heap->span_large_cache + (span_count - 2));
	if (span_cache->count) {
		_rpmalloc_stat_inc(&heap->span_use[span_count - 1].spans_from_cache);
		return span_cache->span[--span_cache->count];
	}
#endif
	return span;
}

static span_t*
_rpmalloc_heap_thread_cache_deferred_extract(heap_t* heap, size_t span_count) {
	span_t* span = 0;
	if (span_count == 1) {
		_rpmalloc_heap_cache_adopt_deferred(heap, &span);
	} else {
		_rpmalloc_heap_cache_adopt_deferred(heap, 0);
		span = _rpmalloc_heap_thread_cache_extract(heap, span_count);
	}
	return span;
}

static span_t*
_rpmalloc_heap_reserved_extract(heap_t* heap, size_t span_count) {
	if (heap->spans_reserved >= span_count)
		return _rpmalloc_span_map(heap, span_count);
	return 0;
}

//! Extract a span from the global cache
static span_t*
_rpmalloc_heap_global_cache_extract(heap_t* heap, size_t span_count) {
#if ENABLE_GLOBAL_CACHE
#if ENABLE_THREAD_CACHE
	span_cache_t* span_cache;
	size_t wanted_count;
	if (span_count == 1) {
		span_cache = &heap->span_cache;
		wanted_count = THREAD_SPAN_CACHE_TRANSFER;
	} else {
		span_cache = (span_cache_t*)(heap->span_large_cache + (span_count - 2));
		wanted_count = THREAD_SPAN_LARGE_CACHE_TRANSFER;
	}
	span_cache->count = _rpmalloc_global_cache_extract_spans(span_cache->span, span_count, wanted_count);
	if (span_cache->count) {
		_rpmalloc_stat_add64(&heap->global_to_thread, span_count * span_cache->count * _memory_span_size);
		_rpmalloc_stat_add(&heap->span_use[span_count - 1].spans_from_global, span_cache->count);
		return span_cache->span[--span_cache->count];
	}
#else
	span_t* span = 0;
	size_t count = _rpmalloc_global_cache_extract_spans(&span, span_count, 1);
	if (count) {
		_rpmalloc_stat_add64(&heap->global_to_thread, span_count * count * _memory_span_size);
		_rpmalloc_stat_add(&heap->span_use[span_count - 1].spans_from_global, count);
		return span;
	}
#endif
#endif
	(void)sizeof(heap);
	(void)sizeof(span_count);
	return 0;
}

static void
_rpmalloc_inc_span_statistics(heap_t* heap, size_t span_count, uint32_t class_idx) {
	(void)sizeof(heap);
	(void)sizeof(span_count);
	(void)sizeof(class_idx);
#if ENABLE_ADAPTIVE_THREAD_CACHE || ENABLE_STATISTICS
	uint32_t idx = (uint32_t)span_count - 1;
	uint32_t current_count = (uint32_t)atomic_incr32(&heap->span_use[idx].current);
	if (current_count > (uint32_t)atomic_load32(&heap->span_use[idx].high))
		atomic_store32(&heap->span_use[idx].high, (int32_t)current_count);
	_rpmalloc_stat_add_peak(&heap->size_class_use[class_idx].spans_current, 1, heap->size_class_use[class_idx].spans_peak);
#endif
}

//! Get a span from one of the cache levels (thread cache, reserved, global cache) or fallback to mapping more memory
static span_t*
_rpmalloc_heap_extract_new_span(heap_t* heap, size_t span_count, uint32_t class_idx) {
	span_t* span;
#if ENABLE_THREAD_CACHE
	if (class_idx < SIZE_CLASS_COUNT) {
		if (heap->size_class[class_idx].cache) {
			span = heap->size_class[class_idx].cache;
			span_t* new_cache = 0;
			if (heap->span_cache.count)
				new_cache = heap->span_cache.span[--heap->span_cache.count];
			heap->size_class[class_idx].cache = new_cache;
			_rpmalloc_inc_span_statistics(heap, span_count, class_idx);
			return span;
		}
	}
#else
	(void)sizeof(class_idx);
#endif
	// Allow 50% overhead to increase cache hits
	size_t base_span_count = span_count;
	size_t limit_span_count = (span_count > 2) ? (span_count + (span_count >> 1)) : span_count;
	if (limit_span_count > LARGE_CLASS_COUNT)
		limit_span_count = LARGE_CLASS_COUNT;
	do {
		span = _rpmalloc_heap_thread_cache_extract(heap, span_count);
		if (EXPECTED(span != 0)) {
			_rpmalloc_stat_inc(&heap->size_class_use[class_idx].spans_from_cache);
			_rpmalloc_inc_span_statistics(heap, span_count, class_idx);
			return span;
		}
		span = _rpmalloc_heap_thread_cache_deferred_extract(heap, span_count);
		if (EXPECTED(span != 0)) {
			_rpmalloc_stat_inc(&heap->size_class_use[class_idx].spans_from_cache);
			_rpmalloc_inc_span_statistics(heap, span_count, class_idx);
			return span;
		}
		span = _rpmalloc_heap_reserved_extract(heap, span_count);
		if (EXPECTED(span != 0)) {
			_rpmalloc_stat_inc(&heap->size_class_use[class_idx].spans_from_reserved);
			_rpmalloc_inc_span_statistics(heap, span_count, class_idx);
			return span;
		}
		span = _rpmalloc_heap_global_cache_extract(heap, span_count);
		if (EXPECTED(span != 0)) {
			_rpmalloc_stat_inc(&heap->size_class_use[class_idx].spans_from_cache);
			_rpmalloc_inc_span_statistics(heap, span_count, class_idx);
			return span;
		}
		++span_count;
	} while (span_count <= limit_span_count);
	//Final fallback, map in more virtual memory
	span = _rpmalloc_span_map(heap, base_span_count);
	_rpmalloc_inc_span_statistics(heap, base_span_count, class_idx);
	_rpmalloc_stat_inc(&heap->size_class_use[class_idx].spans_map_calls);
	return span;
}

static void
_rpmalloc_heap_initialize(heap_t* heap) {
	memset(heap, 0, sizeof(heap_t));
	//Get a new heap ID
	heap->id = 1 + atomic_incr32(&_memory_heap_id);

	//Link in heap in heap ID map
	size_t list_idx = (size_t)heap->id % HEAP_ARRAY_SIZE;
	heap->next_heap = _memory_heaps[list_idx];
	_memory_heaps[list_idx] = heap;
}

static void
_rpmalloc_heap_orphan(heap_t* heap, int first_class) {
	heap->owner_thread = (uintptr_t)-1;
#if RPMALLOC_FIRST_CLASS_HEAPS
	heap_t** heap_list = (first_class ? &_memory_first_class_orphan_heaps : &_memory_orphan_heaps);
#else
	(void)sizeof(first_class);
	heap_t** heap_list = &_memory_orphan_heaps;
#endif
	heap->next_orphan = *heap_list;
	*heap_list = heap;
}

//! Allocate a new heap from newly mapped memory pages
static heap_t*
_rpmalloc_heap_allocate_new(void) {
	// Map in pages for a 16 heaps. If page size is greater than required size for this, map a page and
	// use first part for heaps and remaining part for spans for allocations. Adds a lot of complexity,
	// but saves a lot of memory on systems where page size > 64 spans (4MiB)
	size_t heap_size = sizeof(heap_t);
	size_t aligned_heap_size = 16 * ((heap_size + 15) / 16);
	size_t request_heap_count = 16;
	size_t heap_span_count = ((aligned_heap_size * request_heap_count) + sizeof(span_t) + _memory_span_size - 1) / _memory_span_size;
	size_t block_size = _memory_span_size * heap_span_count;
	size_t span_count = heap_span_count;
	span_t* span = 0;
	// If there are global reserved spans, use these first
	if (_memory_global_reserve_count >= heap_span_count) {
		span = _rpmalloc_global_get_reserved_spans(heap_span_count);
	}
	if (!span) {
		if (_memory_page_size > block_size) {
			span_count = _memory_page_size / _memory_span_size;
			block_size = _memory_page_size;
			// If using huge pages, make sure to grab enough heaps to avoid reallocating a huge page just to serve new heaps
			size_t possible_heap_count = (block_size - sizeof(span_t)) / aligned_heap_size;
			if (possible_heap_count >= (request_heap_count * 16))
				request_heap_count *= 16;
			else if (possible_heap_count < request_heap_count)
				request_heap_count = possible_heap_count;
			heap_span_count = ((aligned_heap_size * request_heap_count) + sizeof(span_t) + _memory_span_size - 1) / _memory_span_size;
		}

		size_t align_offset = 0;
		span = (span_t*)_rpmalloc_mmap(block_size, &align_offset);
		if (!span)
			return 0;

		// Master span will contain the heaps
		_rpmalloc_stat_add(&_reserved_spans, span_count);
		_rpmalloc_stat_inc(&_master_spans);
		_rpmalloc_span_initialize(span, span_count, heap_span_count, align_offset);
	}

	size_t remain_size = _memory_span_size - sizeof(span_t);
	heap_t* heap = (heap_t*)pointer_offset(span, sizeof(span_t));
	_rpmalloc_heap_initialize(heap);

	// Put extra heaps as orphans
	size_t num_heaps = remain_size / aligned_heap_size;
	if (num_heaps < request_heap_count)
		num_heaps = request_heap_count;
	atomic_store32(&heap->child_count, (int32_t)num_heaps - 1);
	heap_t* extra_heap = (heap_t*)pointer_offset(heap, aligned_heap_size);
	while (num_heaps > 1) {
		_rpmalloc_heap_initialize(extra_heap);
		extra_heap->master_heap = heap;
		_rpmalloc_heap_orphan(extra_heap, 1);
		extra_heap = (heap_t*)pointer_offset(extra_heap, aligned_heap_size);
		--num_heaps;
	}

	if (span_count > heap_span_count) {
		// Cap reserved spans
		size_t remain_count = span_count - heap_span_count;
		size_t reserve_count = (remain_count > DEFAULT_SPAN_MAP_COUNT ? DEFAULT_SPAN_MAP_COUNT : remain_count);
		span_t* remain_span = (span_t*)pointer_offset(span, heap_span_count * _memory_span_size);
		_rpmalloc_heap_set_reserved_spans(heap, span, remain_span, reserve_count);

		if (remain_count > reserve_count) {
			// Set to global reserved spans
			remain_span = (span_t*)pointer_offset(remain_span, reserve_count * _memory_span_size);
			reserve_count = remain_count - reserve_count;
			_rpmalloc_global_set_reserved_spans(span, remain_span, reserve_count);
		}
	}

	return heap;
}

static heap_t*
_rpmalloc_heap_extract_orphan(heap_t** heap_list) {
	heap_t* heap = *heap_list;
	*heap_list = (heap ? heap->next_orphan : 0);
	return heap;
}

//! Allocate a new heap, potentially reusing a previously orphaned heap
static heap_t*
_rpmalloc_heap_allocate(int first_class) {
	heap_t* heap = 0;
	while (!atomic_cas32_acquire(&_memory_global_lock, 1, 0))
		_rpmalloc_spin();
	if (first_class == 0)
		heap = _rpmalloc_heap_extract_orphan(&_memory_orphan_heaps);
#if RPMALLOC_FIRST_CLASS_HEAPS
	if (!heap)
		heap = _rpmalloc_heap_extract_orphan(&_memory_first_class_orphan_heaps);
#endif
	if (!heap)
		heap = _rpmalloc_heap_allocate_new();
	atomic_store32_release(&_memory_global_lock, 0);
	_rpmalloc_heap_cache_adopt_deferred(heap, 0);
	return heap;
}

static void
_rpmalloc_heap_release(void* heapptr, int first_class, int release_cache) {
	heap_t* heap = (heap_t*)heapptr;
	if (!heap)
		return;
	//Release thread cache spans back to global cache
	_rpmalloc_heap_cache_adopt_deferred(heap, 0);
	if (release_cache  || heap->finalize) {
#if ENABLE_THREAD_CACHE
		for (size_t iclass = 0; iclass < LARGE_CLASS_COUNT; ++iclass) {
			span_cache_t* span_cache;
			if (!iclass)
				span_cache = &heap->span_cache;
			else
				span_cache = (span_cache_t*)(heap->span_large_cache + (iclass - 1));
			if (!span_cache->count)
				continue;
#if ENABLE_GLOBAL_CACHE
			if (heap->finalize) {
				for (size_t ispan = 0; ispan < span_cache->count; ++ispan)
					_rpmalloc_span_unmap(span_cache->span[ispan]);
			} else {
				_rpmalloc_stat_add64(&heap->thread_to_global, span_cache->count * (iclass + 1) * _memory_span_size);
				_rpmalloc_stat_add(&heap->span_use[iclass].spans_to_global, span_cache->count);
				_rpmalloc_global_cache_insert_spans(span_cache->span, iclass + 1, span_cache->count);
			}
#else
			for (size_t ispan = 0; ispan < span_cache->count; ++ispan)
				_rpmalloc_span_unmap(span_cache->span[ispan]);
#endif
			span_cache->count = 0;
		}
#endif
	}

	if (get_thread_heap_raw() == heap)
		set_thread_heap(0);

#if ENABLE_STATISTICS
	atomic_decr32(&_memory_active_heaps);
	assert(atomic_load32(&_memory_active_heaps) >= 0);
#endif

	// If we are forcibly terminating with _exit the state of the
	// lock atomic is unknown and it's best to just go ahead and exit
	if (get_thread_id() != _rpmalloc_main_thread_id) {
		while (!atomic_cas32_acquire(&_memory_global_lock, 1, 0))
			_rpmalloc_spin();
	}
	_rpmalloc_heap_orphan(heap, first_class);
	atomic_store32_release(&_memory_global_lock, 0);
}

static void
_rpmalloc_heap_release_raw(void* heapptr, int release_cache) {
	_rpmalloc_heap_release(heapptr, 0, release_cache);
}

static void
_rpmalloc_heap_release_raw_fc(void* heapptr) {
	_rpmalloc_heap_release_raw(heapptr, 1);
}

static void
_rpmalloc_heap_finalize(heap_t* heap) {
	if (heap->spans_reserved) {
		span_t* span = _rpmalloc_span_map(heap, heap->spans_reserved);
		_rpmalloc_span_unmap(span);
		heap->spans_reserved = 0;
	}

	_rpmalloc_heap_cache_adopt_deferred(heap, 0);

	for (size_t iclass = 0; iclass < SIZE_CLASS_COUNT; ++iclass) {
		if (heap->size_class[iclass].cache)
			_rpmalloc_span_unmap(heap->size_class[iclass].cache);
		heap->size_class[iclass].cache = 0;
		span_t* span = heap->size_class[iclass].partial_span;
		while (span) {
			span_t* next = span->next;
			_rpmalloc_span_finalize(heap, iclass, span, &heap->size_class[iclass].partial_span);
			span = next;
		}
		// If class still has a free list it must be a full span
		if (heap->size_class[iclass].free_list) {
			span_t* class_span = (span_t*)((uintptr_t)heap->size_class[iclass].free_list & _memory_span_mask);
			span_t** list = 0;
#if RPMALLOC_FIRST_CLASS_HEAPS
			list = &heap->full_span[iclass];
#endif
			--heap->full_span_count;
			if (!_rpmalloc_span_finalize(heap, iclass, class_span, list)) {
				if (list)
					_rpmalloc_span_double_link_list_remove(list, class_span);
				_rpmalloc_span_double_link_list_add(&heap->size_class[iclass].partial_span, class_span);
			}
		}
	}

#if ENABLE_THREAD_CACHE
	for (size_t iclass = 0; iclass < LARGE_CLASS_COUNT; ++iclass) {
		span_cache_t* span_cache;
		if (!iclass)
			span_cache = &heap->span_cache;
		else
			span_cache = (span_cache_t*)(heap->span_large_cache + (iclass - 1));
		for (size_t ispan = 0; ispan < span_cache->count; ++ispan)
			_rpmalloc_span_unmap(span_cache->span[ispan]);
		span_cache->count = 0;
	}
#endif
	assert(!atomic_load_ptr(&heap->span_free_deferred));
}


////////////
///
/// Allocation entry points
///
//////

//! Pop first block from a free list
static void*
free_list_pop(void** list) {
	void* block = *list;
	*list = *((void**)block);
	return block;
}

//! Allocate a small/medium sized memory block from the given heap
static void*
_rpmalloc_allocate_from_heap_fallback(heap_t* heap, uint32_t class_idx) {
	span_t* span = heap->size_class[class_idx].partial_span;
	if (EXPECTED(span != 0)) {
		assert(span->block_count == _memory_size_class[span->size_class].block_count);
		assert(!_rpmalloc_span_is_fully_utilized(span));
		void* block;
		if (span->free_list) {
			//Swap in free list if not empty
			heap->size_class[class_idx].free_list = span->free_list;
			span->free_list = 0;
			block = free_list_pop(&heap->size_class[class_idx].free_list);
		} else {
			//If the span did not fully initialize free list, link up another page worth of blocks			
			void* block_start = pointer_offset(span, SPAN_HEADER_SIZE + ((size_t)span->free_list_limit * span->block_size));
			span->free_list_limit += free_list_partial_init(&heap->size_class[class_idx].free_list, &block,
				(void*)((uintptr_t)block_start & ~(_memory_page_size - 1)), block_start,
				span->block_count - span->free_list_limit, span->block_size);
		}
		assert(span->free_list_limit <= span->block_count);
		span->used_count = span->free_list_limit;

		//Swap in deferred free list if present
		if (atomic_load_ptr(&span->free_list_deferred))
			_rpmalloc_span_extract_free_list_deferred(span);

		//If span is still not fully utilized keep it in partial list and early return block
		if (!_rpmalloc_span_is_fully_utilized(span))
			return block;

		//The span is fully utilized, unlink from partial list and add to fully utilized list
		_rpmalloc_span_double_link_list_pop_head(&heap->size_class[class_idx].partial_span, span);
#if RPMALLOC_FIRST_CLASS_HEAPS
		_rpmalloc_span_double_link_list_add(&heap->full_span[class_idx], span);
#endif
		++heap->full_span_count;
		return block;
	}

	//Find a span in one of the cache levels
	span = _rpmalloc_heap_extract_new_span(heap, 1, class_idx);
	if (EXPECTED(span != 0)) {
		//Mark span as owned by this heap and set base data, return first block
		return _rpmalloc_span_initialize_new(heap, span, class_idx);
	}

	return 0;
}

//! Allocate a small sized memory block from the given heap
static void*
_rpmalloc_allocate_small(heap_t* heap, size_t size) {
	assert(heap);
	//Small sizes have unique size classes
	const uint32_t class_idx = (uint32_t)((size + (SMALL_GRANULARITY - 1)) >> SMALL_GRANULARITY_SHIFT);
	_rpmalloc_stat_inc_alloc(heap, class_idx);
	if (EXPECTED(heap->size_class[class_idx].free_list != 0))
		return free_list_pop(&heap->size_class[class_idx].free_list);
	return _rpmalloc_allocate_from_heap_fallback(heap, class_idx);
}

//! Allocate a medium sized memory block from the given heap
static void*
_rpmalloc_allocate_medium(heap_t* heap, size_t size) {
	assert(heap);
	//Calculate the size class index and do a dependent lookup of the final class index (in case of merged classes)
	const uint32_t base_idx = (uint32_t)(SMALL_CLASS_COUNT + ((size - (SMALL_SIZE_LIMIT + 1)) >> MEDIUM_GRANULARITY_SHIFT));
	const uint32_t class_idx = _memory_size_class[base_idx].class_idx;
	_rpmalloc_stat_inc_alloc(heap, class_idx);
	if (EXPECTED(heap->size_class[class_idx].free_list != 0))
		return free_list_pop(&heap->size_class[class_idx].free_list);
	return _rpmalloc_allocate_from_heap_fallback(heap, class_idx);
}

//! Allocate a large sized memory block from the given heap
static void*
_rpmalloc_allocate_large(heap_t* heap, size_t size) {
	assert(heap);
	//Calculate number of needed max sized spans (including header)
	//Since this function is never called if size > LARGE_SIZE_LIMIT
	//the span_count is guaranteed to be <= LARGE_CLASS_COUNT
	size += SPAN_HEADER_SIZE;
	size_t span_count = size >> _memory_span_size_shift;
	if (size & (_memory_span_size - 1))
		++span_count;

	//Find a span in one of the cache levels
	span_t* span = _rpmalloc_heap_extract_new_span(heap, span_count, SIZE_CLASS_LARGE);
	if (!span)
		return span;

	//Mark span as owned by this heap and set base data
	assert(span->span_count >= span_count);
	span->size_class = SIZE_CLASS_LARGE;
	span->heap = heap;

#if RPMALLOC_FIRST_CLASS_HEAPS
	_rpmalloc_span_double_link_list_add(&heap->large_huge_span, span);
#endif
	++heap->full_span_count;

	return pointer_offset(span, SPAN_HEADER_SIZE);
}

//! Allocate a huge block by mapping memory pages directly
static void*
_rpmalloc_allocate_huge(heap_t* heap, size_t size) {
	assert(heap);
	_rpmalloc_heap_cache_adopt_deferred(heap, 0);
	size += SPAN_HEADER_SIZE;
	size_t num_pages = size >> _memory_page_size_shift;
	if (size & (_memory_page_size - 1))
		++num_pages;
	size_t align_offset = 0;
	span_t* span = (span_t*)_rpmalloc_mmap(num_pages * _memory_page_size, &align_offset);
	if (!span)
		return span;

	//Store page count in span_count
	span->size_class = SIZE_CLASS_HUGE;
	span->span_count = (uint32_t)num_pages;
	span->align_offset = (uint32_t)align_offset;
	span->heap = heap;
	_rpmalloc_stat_add_peak(&_huge_pages_current, num_pages, _huge_pages_peak);

#if RPMALLOC_FIRST_CLASS_HEAPS
	_rpmalloc_span_double_link_list_add(&heap->large_huge_span, span);
#endif
	++heap->full_span_count;

	return pointer_offset(span, SPAN_HEADER_SIZE);
}

//! Allocate a block of the given size
static void*
_rpmalloc_allocate(heap_t* heap, size_t size) {
	_rpmalloc_stat_add64(&_allocation_counter, 1);
	if (EXPECTED(size <= SMALL_SIZE_LIMIT))
		return _rpmalloc_allocate_small(heap, size);
	else if (size <= _memory_medium_size_limit)
		return _rpmalloc_allocate_medium(heap, size);
	else if (size <= LARGE_SIZE_LIMIT)
		return _rpmalloc_allocate_large(heap, size);
	return _rpmalloc_allocate_huge(heap, size);
}

static void*
_rpmalloc_aligned_allocate(heap_t* heap, size_t alignment, size_t size) {
	if (alignment <= SMALL_GRANULARITY)
		return _rpmalloc_allocate(heap, size);

#if ENABLE_VALIDATE_ARGS
	if ((size + alignment) < size) {
		errno = EINVAL;
		return 0;
	}
	if (alignment & (alignment - 1)) {
		errno = EINVAL;
		return 0;
	}
#endif

	if ((alignment <= SPAN_HEADER_SIZE) && (size < _memory_medium_size_limit)) {
		// If alignment is less or equal to span header size (which is power of two),
		// and size aligned to span header size multiples is less than size + alignment,
		// then use natural alignment of blocks to provide alignment
		size_t multiple_size = size ? (size + (SPAN_HEADER_SIZE - 1)) & ~(uintptr_t)(SPAN_HEADER_SIZE - 1) : SPAN_HEADER_SIZE;
		assert(!(multiple_size % SPAN_HEADER_SIZE));
		if (multiple_size <= (size + alignment))
			return _rpmalloc_allocate(heap, multiple_size);
	}

	void* ptr = 0;
	size_t align_mask = alignment - 1;
	if (alignment <= _memory_page_size) {
		ptr = _rpmalloc_allocate(heap, size + alignment);
		if ((uintptr_t)ptr & align_mask) {
			ptr = (void*)(((uintptr_t)ptr & ~(uintptr_t)align_mask) + alignment);
			//Mark as having aligned blocks
			span_t* span = (span_t*)((uintptr_t)ptr & _memory_span_mask);
			span->flags |= SPAN_FLAG_ALIGNED_BLOCKS;
		}
		return ptr;
	}

	// Fallback to mapping new pages for this request. Since pointers passed
	// to rpfree must be able to reach the start of the span by bitmasking of
	// the address with the span size, the returned aligned pointer from this
	// function must be with a span size of the start of the mapped area.
	// In worst case this requires us to loop and map pages until we get a
	// suitable memory address. It also means we can never align to span size
	// or greater, since the span header will push alignment more than one
	// span size away from span start (thus causing pointer mask to give us
	// an invalid span start on free)
	if (alignment & align_mask) {
		errno = EINVAL;
		return 0;
	}
	if (alignment >= _memory_span_size) {
		errno = EINVAL;
		return 0;
	}

	size_t extra_pages = alignment / _memory_page_size;

	// Since each span has a header, we will at least need one extra memory page
	size_t num_pages = 1 + (size / _memory_page_size);
	if (size & (_memory_page_size - 1))
		++num_pages;

	if (extra_pages > num_pages)
		num_pages = 1 + extra_pages;

	size_t original_pages = num_pages;
	size_t limit_pages = (_memory_span_size / _memory_page_size) * 2;
	if (limit_pages < (original_pages * 2))
		limit_pages = original_pages * 2;

	size_t mapped_size, align_offset;
	span_t* span;

retry:
	align_offset = 0;
	mapped_size = num_pages * _memory_page_size;

	span = (span_t*)_rpmalloc_mmap(mapped_size, &align_offset);
	if (!span) {
		errno = ENOMEM;
		return 0;
	}
	ptr = pointer_offset(span, SPAN_HEADER_SIZE);

	if ((uintptr_t)ptr & align_mask)
		ptr = (void*)(((uintptr_t)ptr & ~(uintptr_t)align_mask) + alignment);

	if (((size_t)pointer_diff(ptr, span) >= _memory_span_size) ||
	    (pointer_offset(ptr, size) > pointer_offset(span, mapped_size)) ||
	    (((uintptr_t)ptr & _memory_span_mask) != (uintptr_t)span)) {
		_rpmalloc_unmap(span, mapped_size, align_offset, mapped_size);
		++num_pages;
		if (num_pages > limit_pages) {
			errno = EINVAL;
			return 0;
		}
		goto retry;
	}

	//Store page count in span_count
	span->size_class = SIZE_CLASS_HUGE;
	span->span_count = (uint32_t)num_pages;
	span->align_offset = (uint32_t)align_offset;
	span->heap = heap;
	_rpmalloc_stat_add_peak(&_huge_pages_current, num_pages, _huge_pages_peak);

#if RPMALLOC_FIRST_CLASS_HEAPS
	_rpmalloc_span_double_link_list_add(&heap->large_huge_span, span);
#endif
	++heap->full_span_count;

	_rpmalloc_stat_add64(&_allocation_counter, 1);

	return ptr;
}


////////////
///
/// Deallocation entry points
///
//////

//! Deallocate the given small/medium memory block in the current thread local heap
static void
_rpmalloc_deallocate_direct_small_or_medium(span_t* span, void* block) {
	heap_t* heap = span->heap;
	assert(heap->owner_thread == get_thread_id() || !heap->owner_thread || heap->finalize);
	//Add block to free list
	if (UNEXPECTED(_rpmalloc_span_is_fully_utilized(span))) {
		span->used_count = span->block_count;
#if RPMALLOC_FIRST_CLASS_HEAPS
		_rpmalloc_span_double_link_list_remove(&heap->full_span[span->size_class], span);
#endif
		_rpmalloc_span_double_link_list_add(&heap->size_class[span->size_class].partial_span, span);
		--heap->full_span_count;
	}
	--span->used_count;
	*((void**)block) = span->free_list;
	span->free_list = block;
	if (UNEXPECTED(span->used_count == span->list_size)) {
		_rpmalloc_span_double_link_list_remove(&heap->size_class[span->size_class].partial_span, span);
		_rpmalloc_span_release_to_cache(heap, span);
	}
}

static void
_rpmalloc_deallocate_defer_free_span(heap_t* heap, span_t* span) {
	if (span->size_class != SIZE_CLASS_HUGE)
		_rpmalloc_stat_inc(&heap->span_use[span->span_count - 1].spans_deferred);
	//This list does not need ABA protection, no mutable side state
	do {
		span->free_list = (void*)atomic_load_ptr(&heap->span_free_deferred);
	} while (!atomic_cas_ptr(&heap->span_free_deferred, span, span->free_list));
}

//! Put the block in the deferred free list of the owning span
static void
_rpmalloc_deallocate_defer_small_or_medium(span_t* span, void* block) {
	// The memory ordering here is a bit tricky, to avoid having to ABA protect
	// the deferred free list to avoid desynchronization of list and list size
	// we need to have acquire semantics on successful CAS of the pointer to
	// guarantee the list_size variable validity + release semantics on pointer store
	void* free_list;
	do {
		free_list = atomic_exchange_ptr_acquire(&span->free_list_deferred, INVALID_POINTER);
	} while (free_list == INVALID_POINTER);
	*((void**)block) = free_list;
	uint32_t free_count = ++span->list_size;
	atomic_store_ptr_release(&span->free_list_deferred, block);
	if (free_count == span->block_count) {
		// Span was completely freed by this block. Due to the INVALID_POINTER spin lock
		// no other thread can reach this state simultaneously on this span.
		// Safe to move to owner heap deferred cache
		_rpmalloc_deallocate_defer_free_span(span->heap, span);
	}
}

static void
_rpmalloc_deallocate_small_or_medium(span_t* span, void* p) {
	_rpmalloc_stat_inc_free(span->heap, span->size_class);
	if (span->flags & SPAN_FLAG_ALIGNED_BLOCKS) {
		//Realign pointer to block start
		void* blocks_start = pointer_offset(span, SPAN_HEADER_SIZE);
		uint32_t block_offset = (uint32_t)pointer_diff(p, blocks_start);
		p = pointer_offset(p, -(int32_t)(block_offset % span->block_size));
	}
	//Check if block belongs to this heap or if deallocation should be deferred
#if RPMALLOC_FIRST_CLASS_HEAPS
	int defer = (span->heap->owner_thread && (span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#else
	int defer = ((span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#endif
	if (!defer)
		_rpmalloc_deallocate_direct_small_or_medium(span, p);
	else
		_rpmalloc_deallocate_defer_small_or_medium(span, p);
}

//! Deallocate the given large memory block to the current heap
static void
_rpmalloc_deallocate_large(span_t* span) {
	assert(span->size_class == SIZE_CLASS_LARGE);
	assert(!(span->flags & SPAN_FLAG_MASTER) || !(span->flags & SPAN_FLAG_SUBSPAN));
	assert((span->flags & SPAN_FLAG_MASTER) || (span->flags & SPAN_FLAG_SUBSPAN));
	//We must always defer (unless finalizing) if from another heap since we cannot touch the list or counters of another heap
#if RPMALLOC_FIRST_CLASS_HEAPS
	int defer = (span->heap->owner_thread && (span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#else
	int defer = ((span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#endif
	if (defer) {
		_rpmalloc_deallocate_defer_free_span(span->heap, span);
		return;
	}
	assert(span->heap->full_span_count);
	--span->heap->full_span_count;
#if RPMALLOC_FIRST_CLASS_HEAPS
	_rpmalloc_span_double_link_list_remove(&span->heap->large_huge_span, span);
#endif
#if ENABLE_ADAPTIVE_THREAD_CACHE || ENABLE_STATISTICS
	//Decrease counter
	size_t idx = span->span_count - 1;
	atomic_decr32(&span->heap->span_use[idx].current);
#endif
	heap_t* heap = span->heap;
	assert(heap);
	if ((span->span_count > 1) && !heap->finalize && !heap->spans_reserved) {
		heap->span_reserve = span;
		heap->spans_reserved = span->span_count;
		if (span->flags & SPAN_FLAG_MASTER) {
			heap->span_reserve_master = span;
		} else { //SPAN_FLAG_SUBSPAN
			span_t* master = (span_t*)pointer_offset(span, -(intptr_t)((size_t)span->offset_from_master * _memory_span_size));
			heap->span_reserve_master = master;
			assert(master->flags & SPAN_FLAG_MASTER);
			assert(atomic_load32(&master->remaining_spans) >= (int32_t)span->span_count);
		}
		_rpmalloc_stat_inc(&heap->span_use[idx].spans_to_reserved);
	} else {
		//Insert into cache list
		_rpmalloc_heap_cache_insert(heap, span);
	}
}

//! Deallocate the given huge span
static void
_rpmalloc_deallocate_huge(span_t* span) {
	assert(span->heap);
#if RPMALLOC_FIRST_CLASS_HEAPS
	int defer = (span->heap->owner_thread && (span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#else
	int defer = ((span->heap->owner_thread != get_thread_id()) && !span->heap->finalize);
#endif
	if (defer) {
		_rpmalloc_deallocate_defer_free_span(span->heap, span);
		return;
	}
	assert(span->heap->full_span_count);
	--span->heap->full_span_count;
#if RPMALLOC_FIRST_CLASS_HEAPS
	_rpmalloc_span_double_link_list_remove(&span->heap->large_huge_span, span);
#endif

	//Oversized allocation, page count is stored in span_count
	size_t num_pages = span->span_count;
	_rpmalloc_unmap(span, num_pages * _memory_page_size, span->align_offset, num_pages * _memory_page_size);
	_rpmalloc_stat_sub(&_huge_pages_current, num_pages);
}

//! Deallocate the given block
static void
_rpmalloc_deallocate(void* p) {
	_rpmalloc_stat_add64(&_deallocation_counter, 1);
	//Grab the span (always at start of span, using span alignment)
	span_t* span = (span_t*)((uintptr_t)p & _memory_span_mask);
	if (UNEXPECTED(!span))
		return;
	if (EXPECTED(span->size_class < SIZE_CLASS_COUNT))
		_rpmalloc_deallocate_small_or_medium(span, p);
	else if (span->size_class == SIZE_CLASS_LARGE)
		_rpmalloc_deallocate_large(span);
	else
		_rpmalloc_deallocate_huge(span);
}

////////////
///
/// Reallocation entry points
///
//////

static size_t
_rpmalloc_usable_size(void* p);

//! Reallocate the given block to the given size
static void*
_rpmalloc_reallocate(heap_t* heap, void* p, size_t size, size_t oldsize, unsigned int flags) {
	if (p) {
		//Grab the span using guaranteed span alignment
		span_t* span = (span_t*)((uintptr_t)p & _memory_span_mask);
		if (EXPECTED(span->size_class < SIZE_CLASS_COUNT)) {
			//Small/medium sized block
			assert(span->span_count == 1);
			void* blocks_start = pointer_offset(span, SPAN_HEADER_SIZE);
			uint32_t block_offset = (uint32_t)pointer_diff(p, blocks_start);
			uint32_t block_idx = block_offset / span->block_size;
			void* block = pointer_offset(blocks_start, (size_t)block_idx * span->block_size);
			if (!oldsize)
				oldsize = (size_t)((ptrdiff_t)span->block_size - pointer_diff(p, block));
			if ((size_t)span->block_size >= size) {
				//Still fits in block, never mind trying to save memory, but preserve data if alignment changed
				if ((p != block) && !(flags & RPMALLOC_NO_PRESERVE))
					memmove(block, p, oldsize);
				return block;
			}
		} else if (span->size_class == SIZE_CLASS_LARGE) {
			//Large block
			size_t total_size = size + SPAN_HEADER_SIZE;
			size_t num_spans = total_size >> _memory_span_size_shift;
			if (total_size & (_memory_span_mask - 1))
				++num_spans;
			size_t current_spans = span->span_count;
			void* block = pointer_offset(span, SPAN_HEADER_SIZE);
			if (!oldsize)
				oldsize = (current_spans * _memory_span_size) - (size_t)pointer_diff(p, block) - SPAN_HEADER_SIZE;
			if ((current_spans >= num_spans) && (total_size >= (oldsize / 2))) {
				//Still fits in block, never mind trying to save memory, but preserve data if alignment changed
				if ((p != block) && !(flags & RPMALLOC_NO_PRESERVE))
					memmove(block, p, oldsize);
				return block;
			}
		} else {
			//Oversized block
			size_t total_size = size + SPAN_HEADER_SIZE;
			size_t num_pages = total_size >> _memory_page_size_shift;
			if (total_size & (_memory_page_size - 1))
				++num_pages;
			//Page count is stored in span_count
			size_t current_pages = span->span_count;
			void* block = pointer_offset(span, SPAN_HEADER_SIZE);
			if (!oldsize)
				oldsize = (current_pages * _memory_page_size) - (size_t)pointer_diff(p, block) - SPAN_HEADER_SIZE;
			if ((current_pages >= num_pages) && (num_pages >= (current_pages / 2))) {
				//Still fits in block, never mind trying to save memory, but preserve data if alignment changed
				if ((p != block) && !(flags & RPMALLOC_NO_PRESERVE))
					memmove(block, p, oldsize);
				return block;
			}
		}
	} else {
		oldsize = 0;
	}

	if (!!(flags & RPMALLOC_GROW_OR_FAIL))
		return 0;

	//Size is greater than block size, need to allocate a new block and deallocate the old
	//Avoid hysteresis by overallocating if increase is small (below 37%)
	size_t lower_bound = oldsize + (oldsize >> 2) + (oldsize >> 3);
	size_t new_size = (size > lower_bound) ? size : ((size > oldsize) ? lower_bound : size);
	void* block = _rpmalloc_allocate(heap, new_size);
	if (p && block) {
		if (!(flags & RPMALLOC_NO_PRESERVE))
			memcpy(block, p, oldsize < new_size ? oldsize : new_size);
		_rpmalloc_deallocate(p);
	}

	return block;
}

static void*
_rpmalloc_aligned_reallocate(heap_t* heap, void* ptr, size_t alignment, size_t size, size_t oldsize,
                           unsigned int flags) {
	if (alignment <= SMALL_GRANULARITY)
		return _rpmalloc_reallocate(heap, ptr, size, oldsize, flags);

	int no_alloc = !!(flags & RPMALLOC_GROW_OR_FAIL);
	size_t usablesize = (ptr ? _rpmalloc_usable_size(ptr) : 0);
	if ((usablesize >= size) && !((uintptr_t)ptr & (alignment - 1))) {
		if (no_alloc || (size >= (usablesize / 2)))
			return ptr;
	}
	// Aligned alloc marks span as having aligned blocks
	void* block = (!no_alloc ? _rpmalloc_aligned_allocate(heap, alignment, size) : 0);
	if (EXPECTED(block != 0)) {
		if (!(flags & RPMALLOC_NO_PRESERVE) && ptr) {
			if (!oldsize)
				oldsize = usablesize;
			memcpy(block, ptr, oldsize < size ? oldsize : size);
		}
		_rpmalloc_deallocate(ptr);
	}
	return block;
}


////////////
///
/// Initialization, finalization and utility
///
//////

//! Get the usable size of the given block
static size_t
_rpmalloc_usable_size(void* p) {
	//Grab the span using guaranteed span alignment
	span_t* span = (span_t*)((uintptr_t)p & _memory_span_mask);
	if (span->size_class < SIZE_CLASS_COUNT) {
		//Small/medium block
		void* blocks_start = pointer_offset(span, SPAN_HEADER_SIZE);
		return span->block_size - ((size_t)pointer_diff(p, blocks_start) % span->block_size);
	}
	if (span->size_class == SIZE_CLASS_LARGE) {
		//Large block
		size_t current_spans = span->span_count;
		return (current_spans * _memory_span_size) - (size_t)pointer_diff(p, span);
	}
	//Oversized block, page count is stored in span_count
	size_t current_pages = span->span_count;
	return (current_pages * _memory_page_size) - (size_t)pointer_diff(p, span);
}

//! Adjust and optimize the size class properties for the given class
static void
_rpmalloc_adjust_size_class(size_t iclass) {
	size_t block_size = _memory_size_class[iclass].block_size;
	size_t block_count = (_memory_span_size - SPAN_HEADER_SIZE) / block_size;

	_memory_size_class[iclass].block_count = (uint16_t)block_count;
	_memory_size_class[iclass].class_idx = (uint16_t)iclass;

	//Check if previous size classes can be merged
	if (iclass >= SMALL_CLASS_COUNT) {
		size_t prevclass = iclass;
		while (prevclass > 0) {
			--prevclass;
			//A class can be merged if number of pages and number of blocks are equal
			if (_memory_size_class[prevclass].block_count == _memory_size_class[iclass].block_count)
				memcpy(_memory_size_class + prevclass, _memory_size_class + iclass, sizeof(_memory_size_class[iclass]));
			else
				break;
		}
	}
}

//! Initialize the allocator and setup global data
extern inline int
rpmalloc_initialize(void) {
	if (_rpmalloc_initialized) {
		rpmalloc_thread_initialize();
		return 0;
	}
	return rpmalloc_initialize_config(0);
}

int
rpmalloc_initialize_config(const rpmalloc_config_t* config) {
	if (_rpmalloc_initialized) {
		rpmalloc_thread_initialize();
		return 0;
	}
	_rpmalloc_initialized = 1;

	if (config)
		memcpy(&_memory_config, config, sizeof(rpmalloc_config_t));
	else
		memset(&_memory_config, 0, sizeof(rpmalloc_config_t));

	if (!_memory_config.memory_map || !_memory_config.memory_unmap) {
		_memory_config.memory_map = _rpmalloc_mmap_os;
		_memory_config.memory_unmap = _rpmalloc_unmap_os;
	}

#if RPMALLOC_CONFIGURABLE
	_memory_page_size = _memory_config.page_size;
#else
	_memory_page_size = 0;
#endif
	_memory_huge_pages = 0;
	_memory_map_granularity = _memory_page_size;
	if (!_memory_page_size) {
#if PLATFORM_WINDOWS
		SYSTEM_INFO system_info;
		memset(&system_info, 0, sizeof(system_info));
		GetSystemInfo(&system_info);
		_memory_page_size = system_info.dwPageSize;
		_memory_map_granularity = system_info.dwAllocationGranularity;
#else
		_memory_page_size = (size_t)sysconf(_SC_PAGESIZE);
		_memory_map_granularity = _memory_page_size;
		if (_memory_config.enable_huge_pages) {
#if defined(__linux__)
			size_t huge_page_size = 0;
			FILE* meminfo = fopen("/proc/meminfo", "r");
			if (meminfo) {
				char line[128];
				while (!huge_page_size && fgets(line, sizeof(line) - 1, meminfo)) {
					line[sizeof(line) - 1] = 0;
					if (strstr(line, "Hugepagesize:"))
						huge_page_size = (size_t)strtol(line + 13, 0, 10) * 1024;
				}
				fclose(meminfo);
			}
			if (huge_page_size) {
				_memory_huge_pages = 1;
				_memory_page_size = huge_page_size;
				_memory_map_granularity = huge_page_size;
			}
#elif defined(__FreeBSD__)
			int rc;
			size_t sz = sizeof(rc);

			if (sysctlbyname("vm.pmap.pg_ps_enabled", &rc, &sz, NULL, 0) == 0 && rc == 1) {
				_memory_huge_pages = 1;
				_memory_page_size = 2 * 1024 * 1024;
				_memory_map_granularity = _memory_page_size;
			}
#elif defined(__APPLE__) || defined(__NetBSD__)
			_memory_huge_pages = 1;
			_memory_page_size = 2 * 1024 * 1024;
			_memory_map_granularity = _memory_page_size;
#endif
		}
#endif
	} else {
		if (_memory_config.enable_huge_pages)
			_memory_huge_pages = 1;
	}

#if PLATFORM_WINDOWS
	if (_memory_config.enable_huge_pages) {
		HANDLE token = 0;
		size_t large_page_minimum = GetLargePageMinimum();
		if (large_page_minimum)
			OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &token);
		if (token) {
			LUID luid;
			if (LookupPrivilegeValue(0, SE_LOCK_MEMORY_NAME, &luid)) {
				TOKEN_PRIVILEGES token_privileges;
				memset(&token_privileges, 0, sizeof(token_privileges));
				token_privileges.PrivilegeCount = 1;
				token_privileges.Privileges[0].Luid = luid;
				token_privileges.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
				if (AdjustTokenPrivileges(token, FALSE, &token_privileges, 0, 0, 0)) {
					DWORD err = GetLastError();
					if (err == ERROR_SUCCESS) {
						_memory_huge_pages = 1;
						if (large_page_minimum > _memory_page_size)
						 	_memory_page_size = large_page_minimum;
						if (large_page_minimum > _memory_map_granularity)
							_memory_map_granularity = large_page_minimum;
					}
				}
			}
			CloseHandle(token);
		}
	}
#endif

	size_t min_span_size = 256;
	size_t max_page_size;
#if UINTPTR_MAX > 0xFFFFFFFF
	max_page_size = 4096ULL * 1024ULL * 1024ULL;
#else
	max_page_size = 4 * 1024 * 1024;
#endif
	if (_memory_page_size < min_span_size)
		_memory_page_size = min_span_size;
	if (_memory_page_size > max_page_size)
		_memory_page_size = max_page_size;
	_memory_page_size_shift = 0;
	size_t page_size_bit = _memory_page_size;
	while (page_size_bit != 1) {
		++_memory_page_size_shift;
		page_size_bit >>= 1;
	}
	_memory_page_size = ((size_t)1 << _memory_page_size_shift);

#if RPMALLOC_CONFIGURABLE
	if (!_memory_config.span_size) {
		_memory_span_size = _memory_default_span_size;
		_memory_span_size_shift = _memory_default_span_size_shift;
		_memory_span_mask = _memory_default_span_mask;
	} else {
		size_t span_size = _memory_config.span_size;
		if (span_size > (256 * 1024))
			span_size = (256 * 1024);
		_memory_span_size = 4096;
		_memory_span_size_shift = 12;
		while (_memory_span_size < span_size) {
			_memory_span_size <<= 1;
			++_memory_span_size_shift;
		}
		_memory_span_mask = ~(uintptr_t)(_memory_span_size - 1);
	}
#endif

	_memory_span_map_count = ( _memory_config.span_map_count ? _memory_config.span_map_count : DEFAULT_SPAN_MAP_COUNT);
	if ((_memory_span_size * _memory_span_map_count) < _memory_page_size)
		_memory_span_map_count = (_memory_page_size / _memory_span_size);
	if ((_memory_page_size >= _memory_span_size) && ((_memory_span_map_count * _memory_span_size) % _memory_page_size))
		_memory_span_map_count = (_memory_page_size / _memory_span_size);

	_memory_config.page_size = _memory_page_size;
	_memory_config.span_size = _memory_span_size;
	_memory_config.span_map_count = _memory_span_map_count;
	_memory_config.enable_huge_pages = _memory_huge_pages;

	_memory_span_release_count = (_memory_span_map_count > 4 ? ((_memory_span_map_count < 64) ? _memory_span_map_count : 64) : 4);
	_memory_span_release_count_large = (_memory_span_release_count > 8 ? (_memory_span_release_count / 4) : 2);

#if (defined(__APPLE__) || defined(__HAIKU__)) && ENABLE_PRELOAD
	if (pthread_key_create(&_memory_thread_heap, _rpmalloc_heap_release_raw_fc))
		return -1;
#endif
#if defined(_WIN32) && (!defined(BUILD_DYNAMIC_LINK) || !BUILD_DYNAMIC_LINK)
	fls_key = FlsAlloc(&_rpmalloc_thread_destructor);
#endif

	//Setup all small and medium size classes
	size_t iclass = 0;
	_memory_size_class[iclass].block_size = SMALL_GRANULARITY;
	_rpmalloc_adjust_size_class(iclass);
	for (iclass = 1; iclass < SMALL_CLASS_COUNT; ++iclass) {
		size_t size = iclass * SMALL_GRANULARITY;
		_memory_size_class[iclass].block_size = (uint32_t)size;
		_rpmalloc_adjust_size_class(iclass);
	}
	//At least two blocks per span, then fall back to large allocations
	_memory_medium_size_limit = (_memory_span_size - SPAN_HEADER_SIZE) >> 1;
	if (_memory_medium_size_limit > MEDIUM_SIZE_LIMIT)
		_memory_medium_size_limit = MEDIUM_SIZE_LIMIT;
	for (iclass = 0; iclass < MEDIUM_CLASS_COUNT; ++iclass) {
		size_t size = SMALL_SIZE_LIMIT + ((iclass + 1) * MEDIUM_GRANULARITY);
		if (size > _memory_medium_size_limit)
			break;
		_memory_size_class[SMALL_CLASS_COUNT + iclass].block_size = (uint32_t)size;
		_rpmalloc_adjust_size_class(SMALL_CLASS_COUNT + iclass);
	}

	_memory_orphan_heaps = 0;
#if RPMALLOC_FIRST_CLASS_HEAPS
	_memory_first_class_orphan_heaps = 0;
#endif
	memset(_memory_heaps, 0, sizeof(_memory_heaps));
	atomic_store32_release(&_memory_global_lock, 0);

	//Initialize this thread
	rpmalloc_thread_initialize();
	return 0;
}

//! Finalize the allocator
void
rpmalloc_finalize(void) {
	rpmalloc_thread_finalize(1);
	//rpmalloc_dump_statistics(stdout);

	if (_memory_global_reserve) {
		atomic_add32(&_memory_global_reserve_master->remaining_spans, -(int32_t)_memory_global_reserve_count);
		_memory_global_reserve_master = 0;
		_memory_global_reserve_count = 0;
		_memory_global_reserve = 0;
	}
	atomic_store32_release(&_memory_global_lock, 0);	

	//Free all thread caches and fully free spans
	for (size_t list_idx = 0; list_idx < HEAP_ARRAY_SIZE; ++list_idx) {
		heap_t* heap = _memory_heaps[list_idx];
		while (heap) {
			heap_t* next_heap = heap->next_heap;
			heap->finalize = 1;
			_rpmalloc_heap_global_finalize(heap);
			heap = next_heap;
		}
	}

#if ENABLE_GLOBAL_CACHE
	//Free global caches
	for (size_t iclass = 0; iclass < LARGE_CLASS_COUNT; ++iclass)
		_rpmalloc_global_cache_finalize(&_memory_span_cache[iclass]);
#endif