Re: [PATCH v3 6/8] workingset: memcg: sleep when flushing stats in workingset_refault()

[Michal Koutný]

On Thu, Mar 30, 2023 at 07:17:59PM +0000, Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:
> In workingset_refault(), we call
> mem_cgroup_flush_stats_atomic_ratelimited() to read accurate stats
> within an RCU read section and with sleeping disallowed. Move the
> call above the RCU read section to make it non-atomic.
> 
> Flushing is an expensive operation that scales with the number of cpus
> and the number of cgroups in the system, so avoid doing it atomically
> where possible.

I understand why one does not process the whole flushing load in one go
in general.
However, I remember there were reports of workingset_refault() being
sensitive to latencies (hence the ratelimited call was created).

Is there any consideration on impact of this here?
(Or are there other cond_resched() precendents on this path? Should it
be mentioned like in the vmscan (7/8) commit?)

Thanks,
Michal

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