linux-kernel - Re: [PATCH v2] kvm, mm: account shadow page tables to kmemcg

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Date:   Fri, 29 Jun 2018 09:47:37 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        Linux MM <linux-mm@...ck.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Greg Thelen <gthelen@...gle.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Peter Feiner <pfeiner@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] kvm, mm: account shadow page tables to kmemcg

On Fri, Jun 29, 2018 at 7:55 AM Michal Hocko <mhocko@...nel.org> wrote:
>
> On Fri 29-06-18 16:40:23, Paolo Bonzini wrote:
> > On 29/06/2018 16:30, Michal Hocko wrote:
> > > I am not familiar wtih kvm to judge but if we are going to account this
> > > memory we will probably want to let oom_badness know how much memory
> > > to account to a specific process. Is this something that we can do?
> > > We will probably need a new MM_KERNEL rss_stat stat for that purpose.
> > >
> > > Just to make it clear. I am not opposing to this patch but considering
> > > that shadow page tables might consume a lot of memory it would be good
> > > to know who is responsible for it from the OOM perspective. Something to
> > > solve on top of this.
> >
> > The amount of memory is generally proportional to the size of the
> > virtual machine memory, which is reflected directly into RSS.  Because
> > KVM processes are usually huge, and will probably dwarf everything else
> > in the system (except firefox and chromium of course :)), the general
> > order of magnitude of the oom_badness should be okay.
>
> I think we will need MM_KERNEL longterm anyway. As I've said this is not
> a must for this patch to go. But it is better to have a fair comparision
> and kill larger processes if at all possible. It seems this should be
> the case here.
>

I will look more into MM_KERNEL counter. I still have couple more kmem
allocations in kvm (like dirty bitmap) which I want to be accounted. I
will bundle them together.

thanks,
Shakeel