linux-kernel - Re: [PATCH net-next v2 3/3] sock: Fix improper heuristic on raising memory

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Message-ID: <d1271d557adb68b5f77649861faf470f265e9f6b.camel@redhat.com>
Date:   Thu, 19 Oct 2023 10:53:43 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Abel Wu <wuyun.abel@...edance.com>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Shakeel Butt <shakeelb@...gle.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 3/3] sock: Fix improper heuristic on raising
 memory

On Mon, 2023-10-16 at 21:28 +0800, Abel Wu wrote:
> Before sockets became aware of net-memcg's memory pressure since
> commit e1aab161e013 ("socket: initial cgroup code."), the memory
> usage would be granted to raise if below average even when under
> protocol's pressure. This provides fairness among the sockets of
> same protocol.
> 
> That commit changes this because the heuristic will also be
> effective when only memcg is under pressure which makes no sense.
> Fix this by reverting to the behavior before that commit.
> 
> After this fix, __sk_mem_raise_allocated() no longer considers
> memcg's pressure. As memcgs are isolated from each other w.r.t.
> memory accounting, consuming one's budget won't affect others.
> So except the places where buffer sizes are needed to be tuned,
> allow workloads to use the memory they are provisioned.
> 
> Fixes: e1aab161e013 ("socket: initial cgroup code.")

I think it's better to drop this fixes tag. This is a functional change
and with such tag on at this point of the cycle, will land soon into
every stable tree. That feels not appropriate.

Please repost without such tag, thanks!

You can send the change to stables trees later, if needed.

Paolo