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Re: [PATCH] sched: Fix numabalancing to work with isolated cpus

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On Tue 04-04-17 22:57:28, Srikar Dronamraju wrote:
[...]
> For example:
> perf bench numa mem --no-data_rand_walk -p 4 -t $THREADS -G 0 -P 3072 -T 0 -l 50 -c -s 1000
> would call sched_setaffinity that resets the cpus_allowed mask.
> 
> Cpus_allowed_list:	0-55,57-63,65-71,73-79,81-87,89-175
> Cpus_allowed_list:	0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
> Cpus_allowed_list:	0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
> Cpus_allowed_list:	0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
> Cpus_allowed_list:	0,8,16,24,32,40,48,56,64,72,80,88,96,104,112,120,128,136,144,152,160,168
> 
> The isolated cpus are part of the cpus allowed list. In the above case,
> numabalancing ends up scheduling some of these tasks on isolated cpus.

Why is this bad? If the task is allowed to run on isolated CPUs then why
shouldn't its numa balancing be allowed the same? The changelog
describes what but doesn't explain _why_ this change is needed/useful.
-- 
Michal Hocko
SUSE Labs

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[PATCH] sched: Fix numabalancing to work with isolated cpus Srikar Dronamraju <srikar@linux.vnet.ibm.com> - 2017-04-04 19:30 +0200
  Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Rik van Riel <riel@redhat.com> - 2017-04-04 21:00 +0200
  Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Mel Gorman <mgorman@techsingularity.net> - 2017-04-04 22:40 +0200
    Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Srikar Dronamraju <srikar@linux.vnet.ibm.com> - 2017-04-05 04:00 +0200
      Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Mel Gorman <mgorman@techsingularity.net> - 2017-04-05 10:10 +0200
  Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-05 15:00 +0200
    Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Srikar Dronamraju <srikar@linux.vnet.ibm.com> - 2017-04-05 17:30 +0200
      Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-05 18:50 +0200
        Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Srikar Dronamraju <srikar@linux.vnet.ibm.com> - 2017-04-06 09:30 +0200
          Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-06 09:40 +0200
            Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Peter Zijlstra <peterz@infradead.org> - 2017-04-06 11:30 +0200
              Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-06 12:20 +0200
                Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Peter Zijlstra <peterz@infradead.org> - 2017-04-06 12:40 +0200
                Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-06 12:50 +0200
                Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Peter Zijlstra <peterz@infradead.org> - 2017-04-06 12:50 +0200
                Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Michal Hocko <mhocko@kernel.org> - 2017-04-06 15:50 +0200
  Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Peter Zijlstra <peterz@infradead.org> - 2017-04-06 09:40 +0200
  Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Mike Galbraith <efault@gmx.de> - 2017-04-06 09:40 +0200

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