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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> 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> X-Stat-Signature: qayouw79jnmstosuf6rnk7fc1ss8b96x X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 2C40A40003 X-HE-Tag: 1784637176-930219 X-HE-Meta: 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 EuoP2oDh kanJX1bIzyU5/GIiWvXEgOBc3JpH29Uwrg7nK1taaX5mvUaECBDZp5x+Y7houSRoICrwS6+N8gvciDT+9IZpYELJRYrlcMNvVkrUNfkOn6XSa1pTFVscgZwmm9IHI0HMZ229OFwl+aqbjNXcx80FPeze7yopgJXd45gnc4ahwPjwU9uqA6FrsqjSEQWQHLIlpLe50wWS0w4pYmnek0URQSWSzErnmYGwtPWf9qJc7AlRdwiuSquRnNQxNU4Y9U1YiimizU5p8awgPrytWVvrJotDXycSQsnYtccyShoMqwyCjb1kgC3pyETSB8qhn8LS6gGU8F5v7hlYdC+NPbl2brUmZiMiKn4319SwrwzGX+spGjTBZZpjYdkUt+v+RrPD3COlwIykrUA+7D9E7t806q2Pc4g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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