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bpo-30581: Backport to 3.6: Windows: os.cpu_count() returns wrong number of processors #3267

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Merged
pitrou merged 1 commit into from
Sep 1, 2017
Merged

bpo-30581: Backport to 3.6: Windows: os.cpu_count() returns wrong number of processors #3267

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Windows/2017-08-04-10-05-19.bpo-30581.OQhR7l.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
os.cpu_count() now returns the correct number of processors on Windows
when the number of logical processors is greater than 64.
19 changes: 16 additions & 3 deletions Modules/posixmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11002,9 +11002,22 @@ os_cpu_count_impl(PyObject *module)
{
int ncpu = 0;
#ifdef MS_WINDOWS
SYSTEM_INFO sysinfo;
GetSystemInfo(&sysinfo);
ncpu = sysinfo.dwNumberOfProcessors;
/* Vista is supported and the GetMaximumProcessorCount API is Win7+
Need to fallback to Vista behavior if this call isn't present */
HINSTANCE hKernel32;
hKernel32 = GetModuleHandleW(L"KERNEL32");

static DWORD(CALLBACK *_GetMaximumProcessorCount)(WORD) = NULL;
*(FARPROC*)&_GetMaximumProcessorCount = GetProcAddress(hKernel32,
"GetMaximumProcessorCount");
if (_GetMaximumProcessorCount != NULL) {
ncpu = _GetMaximumProcessorCount(ALL_PROCESSOR_GROUPS);
}
else {
SYSTEM_INFO sysinfo;
GetSystemInfo(&sysinfo);
ncpu = sysinfo.dwNumberOfProcessors;
}
#elif defined(__hpux)
ncpu = mpctl(MPC_GETNUMSPUS, NULL, NULL);
#elif defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
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