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

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Date:   Fri, 16 Jun 2023 11:31:18 +0800
From:   贺中坤 <hezhongkun.hzk@...edance.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     minchan@...nel.org, senozhatsky@...omium.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [RFC PATCH 1/3] zram: charge the compressed RAM to
 the page's memcgroup

On Thu, Jun 15, 2023 at 10:21 PM Michal Hocko <mhocko@...e.com> wrote:
>
> On Thu 15-06-23 22:13:09, 贺中坤 wrote:
> > > This is not really answering my question though. memcg under hard limit
> > > is not really my concern. This is a simpler case. I am not saying it
> > > doesn't need to get addresses but it is the memcg hard limited case that
> > > is much more interested. Because your charges are going to fail very
> > > likely and that would mean that swapout would fail AFAIU. If my
> > > understanding is wrong then it would really help to describe that case
> > > much more in the changelog.
> > >
> >
> > OK, Got it. In many cases I have tested, it  will not fail because we did
> > not charge the page directly，but the objects(like  slab,compressed page),
> > for the zspage may be shared by any memcg.
>
> That sounds like a broken design to me.
> --
> Michal Hocko
> SUSE Labs

I will try more cases in different compression ratios and make sure
that swapout will not fail.