[PATCH] Cygwin: Carry process affinity through to result

[Mark Geisert]

On 3/16/2025 7:09 AM, Christian Franke wrote:
> Mark Geisert wrote:
[...]
> 
> Could only test the single cpu group (aka single physical cpu) case 
> which is the most common, I guess. Works as expected:
> 
> $ uname -r
> 3.6.0-dev-440-g5ec497dc80bc-dirty.x86_64
> 
> $ grep '^model name' /proc/cpuinfo | uniq -c
>       28 model name      : Intel(R) Core(TM) i7-14700K
> 
> $ stress-ng --pthread 1 -v &
> [1] 1323
> ...
> stress-ng: debug: [1324] pthread: [1324] started (instance 0 on CPU 10)
> 
> $ taskset -c -p 1324
> pid 1324's current affinity list: 0-27
> 
> $ taskset -p fff0000 1324 # All E-cores
> pid 1324's current affinity mask: fffffff
> pid 1324's new affinity mask: fff0000
> 
> $ taskset -p fff5555 1324 # All cores but no HT
> pid 1324's current affinity mask: fff0000
> pid 1324's new affinity mask: fff5555
> 
> $ taskset -c -p 8,9 1324 # P-core 4 with HT
> pid 1324's current affinity list: 0,2,4,6,8,10,12,14,16-27
> pid 1324's new affinity list: 8,9
> 
> $ taskset -p 1324
> pid 1324's current affinity mask: 300
> 
> The settings have the desired effect on reported core usage.

Thanks very much Christian for testing.  I want to make a minor change 
to the patch:
     if (procmask == 0)
will be changed to
     if (groupcount > 1)
to make it clearer what's going on.  I will also add a few words to both 
code comments and the patch description saying what will happen on 
systems with more than one cpu group.

It sure would be nice to test on a system with more than 64 h/w threads 
but I don't have that kind of budget ;-).

So, v2 patch incoming shortly.  Comments from other folks welcome.

..mark