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[109.81.80.79]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-495653c8760sm60745635e9.14.2026.07.21.05.32.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2026 05:32:55 -0700 (PDT) Date: Tue, 21 Jul 2026 14:32:54 +0200 From: Michal Hocko To: Andrew Morton Cc: Richard Chang , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Lorenzo Stoakes , Oleg Nesterov , Suren Baghdasaryan , "T . J . Mercier" , Martin Liu , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] mm: vmscan: abort proactive reclaim early when freezing for suspend Message-ID: References: <20260720044103.905191-1-richardycc@google.com> <20260719222306.540829de219e12e21396d260@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260719222306.540829de219e12e21396d260@linux-foundation.org> On Sun 19-07-26 22:23:06, Andrew Morton wrote: > On Mon, 20 Jul 2026 04:41:03 +0000 Richard Chang wrote: > > > Proactive reclaim (triggered via memory.reclaim or node sysfs) checks > > for pending signals in its outer loop in user_proactive_reclaim(). > > However, the inner reclaim loops—specifically scanning cgroups in > > shrink_many() and evicting/aging folios in try_to_shrink_lruvec()—can > > run for a long time before returning to the outer loop, especially on > > systems with many cgroups or large memory sizes. > > > > During system suspend, the PM freezer attempts to freeze all tasks by > > sending fake signals (setting TIF_SIGPENDING). Because the inner loops > > do not check for pending signals, the proactive reclaim task can remain > > stuck in kernel space for seconds, failing to enter the refrigerator in > > a timely manner. This leads to suspend failures due to freeze timeouts, > > a behavior observed on Android devices. > > > > This latency issue is specific to proactive reclaim because of its > > large, user-defined reclaim targets (could be gigabytes). Since commit > > 287d5fedb377 ("mm: memcg: use larger batches for proactive reclaim"), > > proactive reclaim uses larger decaying batch sizes (starting at 1/4 of > > the remaining target) to maintain throughput. This keeps the task in > > the inner reclaim loop for extended periods. In contrast, reactive > > reclaim (global/memcg) uses small targets (SWAP_CLUSTER_MAX, typically > > 32 pages), allowing it to return to the outer loop and check signals > > frequently. > > So 287d5fedb377 led to suspend failures on MGLRU-using kernels. > > That's a regression which justifies a Fixes: and a cc:stable, don't > people agree? I believe this should have both Fixes: 287d5fedb377 and 94968384dde1. -- Michal Hocko SUSE Labs