netdev - Re: [PATCH v2 2/4] sock: Fix misuse of sk_under_memory

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Message-ID: <ZGtlCdQwKw3tr58f@corigine.com>
Date: Mon, 22 May 2023 14:50:17 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Abel Wu <wuyun.abel@...edance.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Glauber Costa <glommer@...allels.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] sock: Fix misuse of sk_under_memory_pressure()

On Mon, May 22, 2023 at 03:01:20PM +0800, Abel Wu wrote:
> The status of global socket memory pressure is updated when:
> 
>   a) __sk_mem_raise_allocated():
> 
> 	enter: sk_memory_allocated(sk) >  sysctl_mem[1]
> 	leave: sk_memory_allocated(sk) <= sysctl_mem[0]
> 
>   b) __sk_mem_reduce_allocated():
> 
> 	leave: sk_under_memory_pressure(sk) &&
> 		sk_memory_allocated(sk) < sysctl_mem[0]
> 
> So the conditions of leaving global pressure are inconstant, which
> may lead to the situation that one pressured net-memcg prevents the
> global pressure from being cleared when there is indeed no global
> pressure, thus the global constrains are still in effect unexpectedly
> on the other sockets.
> 
> This patch fixes this by ignoring the net-memcg's pressure when
> deciding whether should leave global memory pressure.
> 
> Fixes: e1aab161e013 ("socket: initial cgroup code")

really pedantic nit:

Fixes: e1aab161e013 ("socket: initial cgroup code.")

> Signed-off-by: Abel Wu <wuyun.abel@...edance.com>

...