linux-kernel - Re: [RFC PATCH 7/7] memcg: no stock lock for cpu hot-unplug

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Message-ID: <15a8e990-4eb0-489f-bf2f-a192e4fe9543@suse.cz>
Date: Tue, 13 May 2025 15:10:29 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Shakeel Butt <shakeel.butt@...ux.dev>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Muchun Song <muchun.song@...ux.dev>, Alexei Starovoitov <ast@...nel.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Harry Yoo <harry.yoo@...cle.com>, Yosry Ahmed <yosry.ahmed@...ux.dev>,
 bpf@...r.kernel.org, linux-mm@...ck.org, cgroups@...r.kernel.org,
 linux-kernel@...r.kernel.org, Meta kernel team <kernel-team@...a.com>
Subject: Re: [RFC PATCH 7/7] memcg: no stock lock for cpu hot-unplug

On 5/13/25 05:13, Shakeel Butt wrote:
> Previously on the cpu hot-unplug, the kernel would call
> drain_obj_stock() with objcg local lock. However local lock was not
> neede as the stock which was accessed belongs to a dead cpu but we kept

needed

> it there to disable irqs as drain_obj_stock() may call
> mod_objcg_mlstate() which required irqs disabled. However there is no
> need to disable irqs now for mod_objcg_mlstate(), so we can remove the
> lcoal lock altogether from cpu hot-unplug path.

local

> 
> Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>

I think you could switch ordering of this patch with 6/7 to avoid changing
memcg_hotplug_cpu_dead() twice?

Acked-by: Vlastimil Babka <vbabka@...e.cz>