linux-kernel - Re: [RFC PATCH v7 2/2] mm: Fix OOM killer inaccuracy on large many-core systems

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Message-ID: <6hmgutxgdchs4qz6hprwsecwoygwszn5ywixxrvnereilegcsx@mxroaotaw2me>
Date: Thu, 6 Nov 2025 16:32:16 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: kernel test robot <oliver.sang@...el.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	oe-lkp@...ts.linux.dev, lkp@...el.com, Andrew Morton <akpm@...ux-foundation.org>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>, 
	Christoph Lameter <cl@...ux.com>, Martin Liu <liumartin@...gle.com>, 
	David Rientjes <rientjes@...gle.com>, SeongJae Park <sj@...nel.org>, Michal Hocko <mhocko@...e.com>, 
	Johannes Weiner <hannes@...xchg.org>, Sweet Tea Dorminy <sweettea@...gle.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R . Howlett" <liam.howlett@...cle.com>, 
	Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Christian Brauner <brauner@...nel.org>, 
	Wei Yang <richard.weiyang@...il.com>, David Hildenbrand <david@...hat.com>, 
	Miaohe Lin <linmiaohe@...wei.com>, Al Viro <viro@...iv.linux.org.uk>, Yu Zhao <yuzhao@...gle.com>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Mateusz Guzik <mjguzik@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	Aboorva Devarajan <aboorvad@...ux.ibm.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org, christian.koenig@....com
Subject: Re: [RFC PATCH v7 2/2] mm: Fix OOM killer inaccuracy on large
 many-core systems

On Thu, Nov 06, 2025 at 02:53:09PM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "BUG:Bad_rss-counter_state_mm:#type:MM_ANONPAGES_val:#Comm:kworker##Pid" on:
> 
> commit: 25ae03e80acad812e536694c1a07a3f57784ae23 ("[RFC PATCH v7 2/2] mm: Fix OOM killer inaccuracy on large many-core systems")
> url: https://github.com/intel-lab-lkp/linux/commits/Mathieu-Desnoyers/lib-Introduce-hierarchical-per-cpu-counters/20251031-224455
> base: https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-everything
> patch link: https://lore.kernel.org/all/20251031144232.15284-3-mathieu.desnoyers@efficios.com/
> patch subject: [RFC PATCH v7 2/2] mm: Fix OOM killer inaccuracy on large many-core systems
> 
> in testcase: boot
> 
> config: x86_64-randconfig-002-20251103
> compiler: clang-20
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> in fact, we observed various BUG:Bad_rss-counter_state_mm issues for this commit
> but clean on parent, as below
> 
> +------------------------------------------------------------------------+------------+------------+
> |                                                                        | 05880dc4af | 25ae03e80a |
> +------------------------------------------------------------------------+------------+------------+
> | BUG:Bad_rss-counter_state_mm:#type:MM_FILEPAGES_val:#Comm:kworker##Pid | 0          | 10         |
> | BUG:Bad_rss-counter_state_mm:#type:MM_ANONPAGES_val:#Comm:kworker##Pid | 0          | 17         |
> | BUG:Bad_rss-counter_state_mm:#type:MM_ANONPAGES_val:#Comm:swapper_Pid  | 0          | 2          |
> | BUG:Bad_rss-counter_state_mm:#type:MM_ANONPAGES_val:#Comm:modprobe_Pid | 0          | 3          |
> | BUG:Bad_rss-counter_state_mm:#type:MM_FILEPAGES_val:#Comm:modprobe_Pid | 0          | 1          |
> +------------------------------------------------------------------------+------------+------------+
> 
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@...el.com>
> | Closes: https://lore.kernel.org/oe-lkp/202511061432.4e534796-lkp@intel.com
> 
> 
> [   14.858862][   T67] BUG: Bad rss-counter state mm:ffff8881000655c0 type:MM_ANONPAGES val:0 Comm:kworker/u9:0 Pid:67
> [   14.894890][   T69] BUG: Bad rss-counter state mm:ffff888100061cc0 type:MM_FILEPAGES val:0 Comm:kworker/u9:0 Pid:69
> [   14.896108][   T69] BUG: Bad rss-counter state mm:ffff888100061cc0 type:MM_ANONPAGES val:0 Comm:kworker/u9:0 Pid:69

Hmm this shows that percpu_counter_tree_precise_sum() is returning 0 but
percpu_counter_tree_approximate_sum() is off more than
counter->inaccuracy. I have not dig deeper to find why but this needs to
be resolved before considering this series for upstream.