Re: [RFC PATCH 0/2] cpuset: Skip possible unwanted CPU-mask updates.

[Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 11/11/22 10:34, Sebastian Andrzej Siewior wrote:
> On 2022-11-02 09:20:48 [-0400], Waiman Long wrote:
> Hi,
>
>> Yes, that is a known issue which is especially problematic when cgroup v2 is
>> used. That is why I have recently posted a set of patches to enable
>> persistent user requested affinity and they have been merged into tip:
>>
>> 851a723e45d1 sched: Always clear user_cpus_ptr in do_set_cpus_allowed()
>> da019032819a sched: Enforce user requested affinity
>> 8f9ea86fdf99 sched: Always preserve the user requested cpumask
>> 713a2e21a513 sched: Introduce affinity_context
>> 5584e8ac2c68 sched: Add __releases annotations to affine_move_task()
>> They should be able to address the problem that you list here. Please let me
>> know if there are still problem remaining.
> Thank you. This solves the most pressing issue. The CPU-mask is still
> reset upon activation of the cpuset controller.
> This is due to the set_cpus_allowed_ptr() in cpuset_attach().
>
> Is is possible to push these patches stable?

Actually, I prefer to not call set_cpus_allowed_ptr() if the cpumask of 
the old and new cpusets are the same. That will save some cpu cycles. 
Similarly for node_mask. If there is any changes in the cpumask, we have 
to call set_cpus_allowed_ptr(). I will work out a patch to that effect 
when I have spare cycle.

Thanks,
Longman