Message 301150 - Python tracker

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Author	tzickel
Recipients	crwilcox, giampaolo.rodola, paul.moore, pitrou, robbuckley, steve.dower, tim.golden, tzickel, vstinner, zach.ware
Date	2017-09-01.19:52:24
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1504295544.93.0.959220157183.issue30581@psf.upfronthosting.co.za>
In-reply-to

Content
One should be careful with this modification because of the Windows definition of process groups. For example, if multi-threaded code thinks that by reading the value of the new os.cpu_count() it can use all the cores returned, by default it cannot as in windows processes by default can run only in a single process group (how it worked before). We can see such code builtin python stdlib itself: https://github.com/python/cpython/blob/bc61315377056fe362b744d9c44e17cd3178ce54/Lib/concurrent/futures/thread.py#L102 I think even .NET still uses the old way that python did until now: https://github.com/dotnet/corefx/blob/aaaffdf7b8330846f6832f43700fbcc060460c9f/src/System.Runtime.Extensions/src/System/Environment.Windows.cs#L71 Although some of this stuff is used in code for python multiprocess code which that might actually get a boost (since different process can get scheduled to different groups) https://msdn.microsoft.com/en-us/library/windows/desktop/dd405503(v=vs.85).aspx

One should be careful with this modification because of the Windows definition of process groups.

For example, if multi-threaded code thinks that by reading the value of the new os.cpu_count() it can use all the cores returned, by default it cannot as in windows processes by default can run only in a single process group (how it worked before).

We can see such code builtin python stdlib itself:
https://github.com/python/cpython/blob/bc61315377056fe362b744d9c44e17cd3178ce54/Lib/concurrent/futures/thread.py#L102

I think even .NET still uses the old way that python did until now:
https://github.com/dotnet/corefx/blob/aaaffdf7b8330846f6832f43700fbcc060460c9f/src/System.Runtime.Extensions/src/System/Environment.Windows.cs#L71

Although some of this stuff is used in code for python multiprocess code which that might actually get a boost (since different process can get scheduled to different groups)

https://msdn.microsoft.com/en-us/library/windows/desktop/dd405503(v=vs.85).aspx

History
Date	User	Action	Args
2017-09-01 19:52:24	tzickel	set	recipients: + tzickel, paul.moore, pitrou, vstinner, giampaolo.rodola, tim.golden, zach.ware, steve.dower, crwilcox, robbuckley
2017-09-01 19:52:24	tzickel	set	messageid: <1504295544.93.0.959220157183.issue30581@psf.upfronthosting.co.za>
2017-09-01 19:52:24	tzickel	link	issue30581 messages
2017-09-01 19:52:24	tzickel	create