linux-kernel - Re: [RFC PATCH 1/3] zram: charge the compressed RAM to the page's memcgroup

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Message-ID: <CAOUHufZBUEm1P7gm0nFkPSFkNg2fPbs3v3qhL-R9m5yFNoW2YA@mail.gmail.com>
Date:   Wed, 14 Jun 2023 22:59:15 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Zhongkun He <hezhongkun.hzk@...edance.com>
Cc:     minchan@...nel.org, senozhatsky@...omium.org, mhocko@...e.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Fabian Deutsch <fdeutsch@...hat.com>
Subject: Re: [RFC PATCH 1/3] zram: charge the compressed RAM to the page's memcgroup

On Wed, Jun 14, 2023 at 9:48 PM Zhongkun He
<hezhongkun.hzk@...edance.com> wrote:
>
> The compressed RAM is currently charged to kernel, not to
> any memory cgroup, which is not satisfy our usage scenario.
> if the memory of a task is limited by memcgroup, it will
> swap out the memory to zram swap device when the memory
> is insufficient. In that case, the memory limit will have
> no effect.
>
> So, it should makes sense to charge the compressed RAM to
> the page's memory cgroup.

We used to do this a long time ago, but we had per-memcg swapfiles [1[
to prevent compressed pages from different memcgs from sharing the
same zspage.

Does this patchset alone suffer from the same problem, i.e., memcgs
sharing zspages?

[1] https://lwn.net/Articles/592923/