Re: [PATCH] mm: memcg: provide accurate stats for userspace reads

[Shakeel Butt]

On Fri, Aug 11, 2023 at 7:12 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote:
>
[...]
>
> I am worried that writing to a stat for flushing then reading will
> increase the staleness window which we are trying to reduce here.
> Would it be acceptable to add a separate interface to explicitly read
> flushed stats without having to write first? If the distinction
> disappears in the future we can just short-circuit both interfaces.

What is the acceptable staleness time window for your case? It is hard
to imagine that a write+read will always be worse than just a read.
Even the proposed patch can have an unintended and larger than
expected staleness window due to some processing on
return-to-userspace or some scheduling delay.