netdev - Re: [RFC PATCH net-next 0/3] sock: Be aware of memcg pressure on alloc

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Message-ID: <20230914212042.nnubjht3huiap3kk@google.com>
Date: Thu, 14 Sep 2023 21:20:42 +0000
From: Shakeel Butt <shakeelb@...gle.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>, 
	Andrew Morton <akpm@...ux-foundation.org>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Michal Hocko <mhocko@...e.com>, Johannes Weiner <hannes@...xchg.org>, 
	Yosry Ahmed <yosryahmed@...gle.com>, "Matthew Wilcox (Oracle)" <willy@...radead.org>, Yu Zhao <yuzhao@...gle.com>, 
	Kefeng Wang <wangkefeng.wang@...wei.com>, Yafang Shao <laoar.shao@...il.com>, 
	Kuniyuki Iwashima <kuniyu@...zon.com>, Martin KaFai Lau <martin.lau@...nel.org>, 
	Breno Leitao <leitao@...ian.org>, Alexander Mikhalitsyn <alexander@...alicyn.com>, 
	David Howells <dhowells@...hat.com>, Jason Xing <kernelxing@...cent.com>, 
	open list <linux-kernel@...r.kernel.org>, 
	"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>
Subject: Re: [RFC PATCH net-next 0/3] sock: Be aware of memcg pressure on alloc

On Fri, Sep 01, 2023 at 02:21:25PM +0800, Abel Wu wrote:
> 
[...]
> As expected, no obvious performance gain or loss observed. As for the
> issue we encountered, this patchset provides better worst-case behavior
> that such OOM cases are reduced at some extent. While further fine-
> grained traffic control is what the workloads need to think about.
> 

I agree with the motivation but I don't agree with the solution (patch 2
and 3). This is adding one more heuristic in the code which you yourself
described as helped to some extent. In addition adding more dependency
on vmpressure subsystem which is in weird state. Vmpressure is a cgroup
v1 feature which somehow networking subsystem is relying on for cgroup
v2 deployments. In addition vmpressure acts differently for workloads
with different memory types (mapped, mlocked, kernel memory).

Anyways, have you explored the BPF based approach. You can induce socket
pressure at the points you care about and define memory pressure however
your use-case cares for. You can define memory pressure using PSI or
vmpressure or maybe with MEMCG_HIGH events. What do you think?

thanks,
Shakeel