netdev - Re: [PATCH net-next] net-memcg: pass in gfp_t mask to mem_cgroup_charge

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Date:   Wed, 12 Oct 2022 17:17:38 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Wei Wang <weiwan@...gle.com>, Eric Dumazet <edumazet@...gle.com>,
        netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [PATCH net-next] net-memcg: pass in gfp_t mask to mem_cgroup_charge_skmem()

On Wed, Oct 12, 2022 at 4:33 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Tue, 17 Aug 2021 12:40:03 -0700 Wei Wang wrote:
> > Add gfp_t mask as an input parameter to mem_cgroup_charge_skmem(),
> > to give more control to the networking stack and enable it to change
> > memcg charging behavior. In the future, the networking stack may decide
> > to avoid oom-kills when fallbacks are more appropriate.
> >
> > One behavior change in mem_cgroup_charge_skmem() by this patch is to
> > avoid force charging by default and let the caller decide when and if
> > force charging is needed through the presence or absence of
> > __GFP_NOFAIL.
>
> This patch is causing a little bit of pain to us, to workloads running
> with just memory.max set. After this change the TCP rx path no longer
> forces the charging.
>
> Any recommendation for the fix? Setting memory.high a few MB under
> memory.max seems to remove the failures.

Did the revert of this patch fix the issue you are seeing? The reason
I am asking is because this patch should not change the behavior.
Actually someone else reported the similar issue for UDP RX at [1] and
they tested the revert as well. The revert did not fix the issue for
them.

Wei has a better explanation at [2] why this patch is not the cause
for these issues.

[1] https://lore.kernel.org/all/CALvZod5_LVkOkF+gmefnctmx+bRjykSARm2JA9eqKJx85NYBGQ@mail.gmail.com/
[2] https://lore.kernel.org/all/CAEA6p_BhAh6f_kAHEoEJ38nunY=c=4WqxhJQUjT+dCSAr_rm8g@mail.gmail.com/