Merge pull request #1674 from cameron314/bugfix/core-count
Fixed processor count detection on Windows
diff --git a/src/util.cc b/src/util.cc
index 05bdb2d..ae2e3c2 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -487,6 +487,35 @@
int GetProcessorCount() {
#ifdef _WIN32
+#ifndef _WIN64
+ // Need to use GetLogicalProcessorInformationEx to get real core count on
+ // machines with >64 cores. See https://stackoverflow.com/a/31209344/21475
+ DWORD len = 0;
+ if (!GetLogicalProcessorInformationEx(RelationProcessorCore, nullptr, &len)
+ && GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+ std::vector<char> buf(len);
+ int cores = 0;
+ if (GetLogicalProcessorInformationEx(RelationProcessorCore,
+ reinterpret_cast<PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX>(
+ buf.data()), &len)) {
+ for (DWORD i = 0; i < len; ) {
+ auto info = reinterpret_cast<PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX>(
+ buf.data() + i);
+ if (info->Relationship == RelationProcessorCore &&
+ info->Processor.GroupCount == 1) {
+ for (KAFFINITY core_mask = info->Processor.GroupMask[0].Mask;
+ core_mask; core_mask >>= 1) {
+ cores += (core_mask & 1);
+ }
+ }
+ i += info->Size;
+ }
+ if (cores != 0) {
+ return cores;
+ }
+ }
+ }
+#endif
return GetActiveProcessorCount(ALL_PROCESSOR_GROUPS);
#else
// The number of exposed processors might not represent the actual number of
