linux-kernel - Re: [PATCH 1/4] memcg: use mod_node_page

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Message-ID: <aYAmGc6lu973jRwu@linux.dev>
Date: Sun, 1 Feb 2026 20:26:30 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Dev Jain <dev.jain@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, 
	Harry Yoo <harry.yoo@...cle.com>, Qi Zheng <qi.zheng@...ux.dev>, Vlastimil Babka <vbabka@...e.cz>, 
	linux-mm@...ck.org, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Meta kernel team <kernel-team@...a.com>
Subject: Re: [PATCH 1/4] memcg: use mod_node_page_state to update stats

On Thu, Jan 29, 2026 at 06:35:21PM +0530, Dev Jain wrote:
> 
> On 11/11/25 4:50 am, Shakeel Butt wrote:
> > The memcg stats are safe against irq (and nmi) context and thus does not
> > require disabling irqs. However some code paths for memcg stats also
> > update the node level stats and use irq unsafe interface and thus
> > require the users to disable irqs. However node level stats, on
> > architectures with HAVE_CMPXCHG_LOCAL (all major ones), has interface
> > which does not require irq disabling. Let's move memcg stats code to
> > start using that interface for node level stats.
> >
> > Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
> > ---
> 
> Hello Shakeel,
> 
> We are seeing a regression in micromm/munmap benchmark with this patch, on arm64 -
> the benchmark mmmaps a lot of memory, memsets it, and measures the time taken
> to munmap. Please see below if my understanding of this patch is correct.

Thanks for the report. Are you seeing regression in just the benchmark
or some real workload as well? Also how much regression are you seeing?
I have a kernel rebot regression report [1] for this patch as well which
says 2.6% regression and thus it was on the back-burner for now. I will
take look at this again soon.

[1] https://lore.kernel.org/all/202512101408.af3876df-lkp@intel.com/