| #define JEMALLOC_EXTENT_DSS_C_ |
| #include "jemalloc/internal/jemalloc_internal.h" |
| /******************************************************************************/ |
| /* Data. */ |
| |
| const char *opt_dss = DSS_DEFAULT; |
| |
| const char *dss_prec_names[] = { |
| "disabled", |
| "primary", |
| "secondary", |
| "N/A" |
| }; |
| |
| /* |
| * Current dss precedence default, used when creating new arenas. NB: This is |
| * stored as unsigned rather than dss_prec_t because in principle there's no |
| * guarantee that sizeof(dss_prec_t) is the same as sizeof(unsigned), and we use |
| * atomic operations to synchronize the setting. |
| */ |
| static unsigned dss_prec_default = (unsigned)DSS_PREC_DEFAULT; |
| |
| /* Base address of the DSS. */ |
| static void *dss_base; |
| /* Atomic boolean indicating whether the DSS is exhausted. */ |
| static unsigned dss_exhausted; |
| /* Atomic current upper limit on DSS addresses. */ |
| static void *dss_max; |
| |
| /******************************************************************************/ |
| |
| static void * |
| extent_dss_sbrk(intptr_t increment) |
| { |
| #ifdef JEMALLOC_DSS |
| return (sbrk(increment)); |
| #else |
| not_implemented(); |
| return (NULL); |
| #endif |
| } |
| |
| dss_prec_t |
| extent_dss_prec_get(void) |
| { |
| dss_prec_t ret; |
| |
| if (!have_dss) |
| return (dss_prec_disabled); |
| ret = (dss_prec_t)atomic_read_u(&dss_prec_default); |
| return (ret); |
| } |
| |
| bool |
| extent_dss_prec_set(dss_prec_t dss_prec) |
| { |
| if (!have_dss) |
| return (dss_prec != dss_prec_disabled); |
| atomic_write_u(&dss_prec_default, (unsigned)dss_prec); |
| return (false); |
| } |
| |
| static void * |
| extent_dss_max_update(void *new_addr) |
| { |
| void *max_cur; |
| spin_t spinner; |
| |
| /* |
| * Get the current end of the DSS as max_cur and assure that dss_max is |
| * up to date. |
| */ |
| spin_init(&spinner); |
| while (true) { |
| void *max_prev = atomic_read_p(&dss_max); |
| |
| max_cur = extent_dss_sbrk(0); |
| if ((uintptr_t)max_prev > (uintptr_t)max_cur) { |
| /* |
| * Another thread optimistically updated dss_max. Wait |
| * for it to finish. |
| */ |
| spin_adaptive(&spinner); |
| continue; |
| } |
| if (!atomic_cas_p(&dss_max, max_prev, max_cur)) |
| break; |
| } |
| /* Fixed new_addr can only be supported if it is at the edge of DSS. */ |
| if (new_addr != NULL && max_cur != new_addr) |
| return (NULL); |
| |
| return (max_cur); |
| } |
| |
| void * |
| extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size, |
| size_t alignment, bool *zero, bool *commit) |
| { |
| extent_t *gap; |
| |
| cassert(have_dss); |
| assert(size > 0); |
| assert(alignment > 0); |
| |
| /* |
| * sbrk() uses a signed increment argument, so take care not to |
| * interpret a large allocation request as a negative increment. |
| */ |
| if ((intptr_t)size < 0) |
| return (NULL); |
| |
| gap = extent_alloc(tsdn, arena); |
| if (gap == NULL) |
| return (NULL); |
| |
| if (!atomic_read_u(&dss_exhausted)) { |
| /* |
| * The loop is necessary to recover from races with other |
| * threads that are using the DSS for something other than |
| * malloc. |
| */ |
| while (true) { |
| void *ret, *max_cur, *gap_addr, *dss_next, *dss_prev; |
| size_t gap_size; |
| intptr_t incr; |
| |
| max_cur = extent_dss_max_update(new_addr); |
| if (max_cur == NULL) |
| goto label_oom; |
| |
| /* |
| * Compute how much gap space (if any) is necessary to |
| * satisfy alignment. This space can be recycled for |
| * later use. |
| */ |
| gap_addr = (void *)(PAGE_CEILING((uintptr_t)max_cur)); |
| ret = (void *)ALIGNMENT_CEILING((uintptr_t)gap_addr, |
| PAGE_CEILING(alignment)); |
| gap_size = (uintptr_t)ret - (uintptr_t)gap_addr; |
| if (gap_size != 0) { |
| extent_init(gap, arena, gap_addr, gap_size, |
| gap_size, arena_extent_sn_next(arena), |
| false, false, true, false); |
| } |
| dss_next = (void *)((uintptr_t)ret + size); |
| if ((uintptr_t)ret < (uintptr_t)max_cur || |
| (uintptr_t)dss_next < (uintptr_t)max_cur) |
| goto label_oom; /* Wrap-around. */ |
| incr = gap_size + size; |
| |
| /* |
| * Optimistically update dss_max, and roll back below if |
| * sbrk() fails. No other thread will try to extend the |
| * DSS while dss_max is greater than the current DSS |
| * max reported by sbrk(0). |
| */ |
| if (atomic_cas_p(&dss_max, max_cur, dss_next)) |
| continue; |
| |
| /* Try to allocate. */ |
| dss_prev = extent_dss_sbrk(incr); |
| if (dss_prev == max_cur) { |
| /* Success. */ |
| if (gap_size != 0) |
| extent_dalloc_gap(tsdn, arena, gap); |
| else |
| extent_dalloc(tsdn, arena, gap); |
| if (!*commit) |
| *commit = pages_decommit(ret, size); |
| if (*zero && *commit) { |
| extent_hooks_t *extent_hooks = |
| EXTENT_HOOKS_INITIALIZER; |
| extent_t extent; |
| |
| extent_init(&extent, arena, ret, size, |
| size, 0, true, false, true, false); |
| if (extent_purge_forced_wrapper(tsdn, |
| arena, &extent_hooks, &extent, 0, |
| size)) |
| memset(ret, 0, size); |
| } |
| return (ret); |
| } |
| /* |
| * Failure, whether due to OOM or a race with a raw |
| * sbrk() call from outside the allocator. Try to roll |
| * back optimistic dss_max update; if rollback fails, |
| * it's due to another caller of this function having |
| * succeeded since this invocation started, in which |
| * case rollback is not necessary. |
| */ |
| atomic_cas_p(&dss_max, dss_next, max_cur); |
| if (dss_prev == (void *)-1) { |
| /* OOM. */ |
| atomic_write_u(&dss_exhausted, (unsigned)true); |
| goto label_oom; |
| } |
| } |
| } |
| label_oom: |
| extent_dalloc(tsdn, arena, gap); |
| return (NULL); |
| } |
| |
| static bool |
| extent_in_dss_helper(void *addr, void *max) |
| { |
| return ((uintptr_t)addr >= (uintptr_t)dss_base && (uintptr_t)addr < |
| (uintptr_t)max); |
| } |
| |
| bool |
| extent_in_dss(void *addr) |
| { |
| cassert(have_dss); |
| |
| return (extent_in_dss_helper(addr, atomic_read_p(&dss_max))); |
| } |
| |
| bool |
| extent_dss_mergeable(void *addr_a, void *addr_b) |
| { |
| void *max; |
| |
| cassert(have_dss); |
| |
| if ((uintptr_t)addr_a < (uintptr_t)dss_base && (uintptr_t)addr_b < |
| (uintptr_t)dss_base) |
| return (true); |
| |
| max = atomic_read_p(&dss_max); |
| return (extent_in_dss_helper(addr_a, max) == |
| extent_in_dss_helper(addr_b, max)); |
| } |
| |
| void |
| extent_dss_boot(void) |
| { |
| cassert(have_dss); |
| |
| dss_base = extent_dss_sbrk(0); |
| dss_exhausted = (unsigned)(dss_base == (void *)-1); |
| dss_max = dss_base; |
| } |
| |
| /******************************************************************************/ |