Re: Implement sched_[gs]etaffinity()

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Apr 11 10:25, Corinna Vinschen wrote:
> Hi Mark,
> 
> On Apr 10 21:21, Mark Geisert wrote:
> > I've recently sent a patch to cygwin-patches that implements these
> > Linux-specific functions.  I used the following test program to debug and
> > test the implementation.  When the program is run, you can watch it migrate
> > from CPU to CPU with Windows Task Manager.
> > 
> > I've only tested on 64-bit Windows 7 so far.  If the code (in the patch) is
> > adequate I will supply another patch for doc updates, etc.
> 
> Your patch is nicely done, but what about machines with more than 64
> CPUs?  Your patch only uses the standard API for up to 64 CPUs, so a
> process can never use more than 64 CPUs or use CPUs from different CPU
> groups.  There was also the case of this weird machine Achim Gratz once
> worked on, which had less than 64 CPUs but *still* used multiple CPU
> groups under Windows, for some reason.
> 
> Any chance you could update your patch to support this functionality?
> For some info, see MSDN:
> 
> https://docs.microsoft.com/en-us/windows/desktop/ProcThread/processor-groups
> 
> Also, there's already some code in fhandler_proc.cc, function
> format_proc_cpuinfo to handle CPU groups.  You can use the
> wincap.has_processor_groups() method to check if the system
> supports CPU groups.

Btw., Glibc's cpu_set_t supports up to 1024 CPUs.  See
https://sourceware.org/git/?p=glibc.git;a=blob;f=posix/bits/cpu-set.h
This may be ok for the foreseable future, I guess.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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