Re: Implement sched_[gs]etaffinity()

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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On Apr 11 13:52, Mark Geisert wrote:
> On Thu, 11 Apr 2019, Corinna Vinschen wrote:
> > 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.
> 
> Hi Corinna,
> I will look into CPU group support; thanks for the pointers.  I also need to
> fix the assumption I made about which flavor of pid would be handed to the
> functions.. they will be Cygwin pids but need conversion to Windows pids
> internally.

Yeah, right, I missed to notice that.  I'll add a few notes inline
over @ cygwin-patches.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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