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GeezerVison is showing github.com — bpo-30581: Windows: os.cpu_count() returns wrong number of processors by crwilcox · Pull Request #2934 · python/cpython

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crwilcox commented Jul 28, 2017 •

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os.cpu_count() returns wrong number of processors on system with > 64 logical processors

https://bugs.python.org/issue30581

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the-knights-who-say-ni commented Jul 28, 2017

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Hello, and thanks for your contribution!

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Unfortunately we couldn't find an account corresponding to your GitHub username on bugs.python.org (b.p.o) to verify you have signed the CLA (this might be simply due to a missing "GitHub Name" entry in your b.p.o account settings). This is necessary for legal reasons before we can look at your contribution. Please follow the steps outlined in the CPython devguide to rectify this issue.

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the-knights-who-say-ni added the CLA not signed label

Jul 28, 2017


          Fixes python#30581 by adding a path to use newer GetMaximumProcessorC…

73adde2

…ount API on Windows calls to os.cpu_count()

crwilcox force-pushed the bug/windows-processor-counts branch from 7e6a49c to 73adde2 Compare

July 28, 2017 16:46

pitrou reviewed

Jul 29, 2017

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Modules/posixmodule.c

		/* 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");

pitrou Jul 29, 2017

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Does the handle need to be closed after using it?

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crwilcox Jul 29, 2017

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Other places in posixmodule use this but on closer inspection they are all in methods.

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zooba Aug 2, 2017

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No, GetModuleHandle does not increase the refcount on the module (it also only works on already-loaded modules, but kernel32 is guaranteed to be there).

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pitrou reviewed

Jul 29, 2017

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Modules/posixmodule.c

		(FARPROC)&_GetMaximumProcessorCount = GetProcAddress(hKernel32,
		"GetMaximumProcessorCount");
		if (_GetMaximumProcessorCount != NULL) {
		ncpu = _GetMaximumProcessorCount(ALL_PROCESSOR_GROUPS);

pitrou Jul 29, 2017

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Is ALL_PROCESSOR_GROUPS always defined at compile-time, even before Windows 7?

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crwilcox Jul 29, 2017

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I think this may be just windows 7 forward. I know the result needs to run on Pre-Windows 7, does it also need to compile?

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zooba Aug 2, 2017

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In the Windows 10 SDK (which is required) the symbol is always defined. We filter APIs to those available on Vista, but that symbol is not excluded when you do that.

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pitrou requested a review from zooba

July 29, 2017 10:16

Mariatta removed the CLA not signed label

Jul 31, 2017

the-knights-who-say-ni added the CLA signed label

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This still requires a NEWS.d entry, and the documentation should be updated to indicate:

the behaviour of the function has changed on Windows
the fact that a 32-bit interpreter on 64-bit Windows will never return (nor have access to) more than 32 CPUs

I don't believe the latter point is a problem - the current behaviour of the API has the same issue. This falls into the same category as sys.getwindowsversion() reporting what the operating system provides, even when this is incorrect (e.g. Python 2.7 will always return 6.2 even on Windows 10, and the OS also shims certain APIs to behave like the previous version). Since the process is limited by the OS to only 32 CPUs, the os module API should reflect that limit.

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          Add NEWS.d entry for bpo-30581, os.cpu_count on Windows.

ef1b704

giampaolo commented Aug 4, 2017

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Before merging please consider my comment here:
http://bugs.python.org/issue30581#msg299477

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crwilcox commented Aug 4, 2017

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@giampaolo, I had responded. Is there something I didn't address?

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pitrou commented Aug 29, 2017

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@giampaolo, do you have more concerns here?

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giampaolo commented Aug 30, 2017

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Sorry for the delay (I've been backpacking / travelling through China).
Considering os.cpu_count() is not supposed to return the number of usable CPUs (as I first erroneously thought) the patch LGTM.

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giampaolo approved these changes

Aug 30, 2017

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Aug 30, 2017


          Tweak NEWS entry

780ea3c

pitrou merged commit c67bae0 into python:master

Aug 30, 2017

pitrou commented Aug 30, 2017

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Thank you @crwilcox !

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crwilcox added a commit to crwilcox/cpython that referenced this pull request

Sep 1, 2017


          bpo-30581: Windows: os.cpu_count() returns wrong number of processors (…

e6374bc

…python#2934)

* Fixes python#30581 by adding a path to use newer GetMaximumProcessorCount API on Windows calls to os.cpu_count()

* Add NEWS.d entry for bpo-30581, os.cpu_count on Windows.

* Tweak NEWS entry

crwilcox mentioned this pull request

Sep 1, 2017

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

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pitrou pushed a commit that referenced this pull request

Sep 1, 2017


          bpo-30581: Windows: os.cpu_count() returns wrong number of processors (…

58521fd

…#2934) (#3267)

* Fixes #30581 by adding a path to use newer GetMaximumProcessorCount API on Windows calls to os.cpu_count()

* Add NEWS.d entry for bpo-30581, os.cpu_count on Windows.

* Tweak NEWS entry

GadgetSteve pushed a commit to GadgetSteve/cpython that referenced this pull request

Sep 10, 2017


          bpo-30581: Windows: os.cpu_count() returns wrong number of processors (…

2da135d

…python#2934)

* Fixes python#30581 by adding a path to use newer GetMaximumProcessorCount API on Windows calls to os.cpu_count()

* Add NEWS.d entry for bpo-30581, os.cpu_count on Windows.

* Tweak NEWS entry

Mariatta removed the awaiting merge label

Oct 8, 2017

arhadthedev changed the title ~~bpo-30581: Windows: os.cpu_count() returns wrong number of processors~~ empty

Apr 25, 2023

arhadthedev changed the title ~~empty~~ bpo-30581: Windows: os.cpu_count() returns wrong number of processors

Apr 25, 2023

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crwilcox commented Jul 28, 2017 • edited by bedevere-bot Loading Uh oh! There was an error while loading. Please reload this page.

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the-knights-who-say-ni commented Jul 28, 2017

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giampaolo commented Aug 4, 2017

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crwilcox commented Jul 28, 2017 •

edited by bedevere-bot

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