Re: Implement sched_[gs]etaffinity()

[Mark Geisert <mark@maxrnd.com>]

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.

..mark