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authorGravatar Abseil Team <absl-team@google.com>2021-04-13 10:34:23 -0700
committerGravatar Dino Radaković <dinor@google.com>2021-04-13 16:57:41 -0700
commit25bc82d7ef481bd06723aae805d286eba81900ca (patch)
treec3a878e5cbd2f8426cbc43ffad8c1f0655cd34a5 /absl/base
parentb97a1ecda869ca8754d467a56c50275cebfeb328 (diff)
Export of internal Abseil changes
-- f09549625d7417fca379ff68334379d281480608 by Martijn Vels <mvels@google.com>: Fix GetNumCPUs() for WIN32 platforms PiperOrigin-RevId: 368245360 -- e903c6690d0568f80356e03b07a895b031553977 by Abseil Team <absl-team@google.com>: Optimize `Cord::InlineRep::InlineRep(Cord::InlineRep&& src)`. PiperOrigin-RevId: 368198990 GitOrigin-RevId: f09549625d7417fca379ff68334379d281480608 Change-Id: I2d750c8c87f2804335a60ba8db949dedfaa462e2
Diffstat (limited to 'absl/base')
-rw-r--r--absl/base/internal/sysinfo.cc67
1 files changed, 67 insertions, 0 deletions
diff --git a/absl/base/internal/sysinfo.cc b/absl/base/internal/sysinfo.cc
index 4a3b2050..08a1e288 100644
--- a/absl/base/internal/sysinfo.cc
+++ b/absl/base/internal/sysinfo.cc
@@ -61,9 +61,76 @@ namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {
+namespace {
+
+#if defined(_WIN32)
+
+// Returns number of bits set in `bitMask`
+DWORD Win32CountSetBits(ULONG_PTR bitMask) {
+ for (DWORD bitSetCount = 0; ; ++bitSetCount) {
+ if (bitMask == 0) return bitSetCount;
+ bitMask &= bitMask - 1;
+ }
+}
+
+// Returns the number of logical CPUs using GetLogicalProcessorInformation(), or
+// 0 if the number of processors is not available or can not be computed.
+// https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getlogicalprocessorinformation
+int Win32NumCPUs() {
+#pragma comment(lib, "kernel32.lib")
+ using Info = SYSTEM_LOGICAL_PROCESSOR_INFORMATION;
+
+ DWORD info_size = sizeof(Info);
+ Info* info(static_cast<Info*>(malloc(info_size)));
+ if (info == nullptr) return 0;
+
+ bool success = GetLogicalProcessorInformation(info, &info_size);
+ if (!success && GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+ free(info);
+ info = static_cast<Info*>(malloc(info_size));
+ if (info == nullptr) return 0;
+ success = GetLogicalProcessorInformation(info, &info_size);
+ }
+
+ DWORD logicalProcessorCount = 0;
+ if (success) {
+ Info* ptr = info;
+ DWORD byteOffset = 0;
+ while (byteOffset + sizeof(Info) <= info_size) {
+ switch (ptr->Relationship) {
+ case RelationProcessorCore:
+ logicalProcessorCount += Win32CountSetBits(ptr->ProcessorMask);
+ break;
+
+ case RelationNumaNode:
+ case RelationCache:
+ case RelationProcessorPackage:
+ // Ignore other entries
+ break;
+
+ default:
+ // Ignore unknown entries
+ break;
+ }
+ byteOffset += sizeof(Info);
+ ptr++;
+ }
+ }
+ free(info);
+ return logicalProcessorCount;
+}
+
+#endif
+
+} // namespace
+
+
static int GetNumCPUs() {
#if defined(__myriad2__)
return 1;
+#elif defined(_WIN32)
+ const unsigned hardware_concurrency = Win32NumCPUs();
+ return hardware_concurrency ? hardware_concurrency : 1;
#else
// Other possibilities:
// - Read /sys/devices/system/cpu/online and use cpumask_parse()