linux-kernel - Re: [PATCH] memcg: accounting for objects allocated for new netdevice

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Message-ID: <CALvZod6Dz7iw=gyiQ2pDVe2RJxF-7PbVoptwFZCw=sWtxpBBGQ@mail.gmail.com>
Date:   Wed, 27 Apr 2022 09:52:25 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Vasily Averin <vvs@...nvz.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Vlastimil Babka <vbabka@...e.cz>, kernel@...nvz.org,
        Florian Westphal <fw@...len.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        Cgroups <cgroups@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <tj@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] memcg: accounting for objects allocated for new netdevice

On Wed, Apr 27, 2022 at 7:01 AM Michal Koutný <mkoutny@...e.com> wrote:
>
> Hello Vasily.
>
> On Wed, Apr 27, 2022 at 01:37:50PM +0300, Vasily Averin <vvs@...nvz.org> wrote:
> > diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
> > index cfa79715fc1a..2881aeeaa880 100644
> > --- a/fs/kernfs/mount.c
> > +++ b/fs/kernfs/mount.c
> > @@ -391,7 +391,7 @@ void __init kernfs_init(void)
> >  {
> >       kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
> >                                             sizeof(struct kernfs_node),
> > -                                           0, SLAB_PANIC, NULL);
> > +                                           0, SLAB_PANIC | SLAB_ACCOUNT, NULL);
>
> kernfs accounting you say?
> kernfs backs up also cgroups, so the parent-child accounting comes to my
> mind.
> See the temporary switch to parent memcg in mem_cgroup_css_alloc().
>
> (I mean this makes some sense but I'd suggest unlumping the kernfs into
> a separate path for possible discussion and its not-only-netdevice
> effects.)
>

I agree with Michal that kernfs accounting should be its own patch.
Internally at Google, we actually have enabled the memcg accounting of
kernfs nodes. We have workloads which create 100s of subcontainers and
without memcg accounting of kernfs we see high system overhead.