From: Johannes Weiner <hannes@cmpxchg.org>
To: Breno Leitao <leitao@debian.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Qi Zheng <qi.zheng@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Lorenzo Stoakes <ljs@kernel.org>,
Kairui Song <kasong@tencent.com>, Barry Song <baohua@kernel.org>,
Axel Rasmussen <axelrasmussen@google.com>,
Yuanchu Xie <yuanchu@google.com>, Wei Xu <weixugc@google.com>,
paulmck@kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com,
stable@vger.kernel.org
Subject: Re: [PATCH] mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec()
Date: Mon, 10 Aug 2026 16:02:09 -0400 [thread overview]
Message-ID: <anouQR89Q-pDAfyt@cmpxchg.org> (raw)
In-Reply-To: <20260810-rcu_task_shrink_lruvec-v1-1-4d9f7d5251cb@debian.org>
On Mon, Aug 10, 2026 at 02:57:36AM -0700, Breno Leitao wrote:
> I am seeing some rcu_tasks stalls in the Meta fleet during reclaim.
>
> INFO: rcu_tasks detected stalls on tasks:
> 0000000088620d09: .. nvcsw: 6735/6735 holdout: 1 idle_cpu: -1/8
> task:GlobalCPUThread state:R running task pid:2552016 tgid:2524552
> Call Trace:
> shrink_lruvec
> mem_cgroup_iter
> shrink_node
> do_try_to_free_pages
> try_to_free_pages
> __alloc_frozen_pages_noprof
> alloc_pages_noprof
> pte_alloc_one
> __pte_alloc
> handle_mm_fault
>
> Nothing promises direct reclaim returns in bounded time, and the scan
> loop in shrink_lruvec() only calls cond_resched(), which is a no-op on
> PREEMPTION kernels. Involuntary preemption is not a Tasks-RCU
> quiescent state, so the reclaiming task never reports one and becomes a
> holdout.
>
> Upgrade it to cond_resched_tasks_rcu_qs(), which reports a quiescent
> state even when cond_resched() does nothing.
>
> PS: This has been discussed in [1]
>
> Link: https://lore.kernel.org/all/amdWVTs0WKOxguxP@gmail.com/ [1]
> Cc: stable@vger.kernel.org
> Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
next prev parent reply other threads:[~2026-08-10 20:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-10 9:57 [PATCH] mm/vmscan: report RCU-tasks quiescent states in shrink_lruvec() Breno Leitao
2026-08-10 15:38 ` Paul E. McKenney
2026-08-10 20:02 ` Johannes Weiner [this message]
2026-08-11 4:43 ` Shakeel Butt
2026-08-11 17:38 ` Paul E. McKenney
2026-08-11 17:54 ` Shakeel Butt
2026-08-11 18:39 ` Paul E. McKenney
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