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Fri, 27 Mar 2026 09:41:10 -0700 (PDT) Received: from localhost ([2603:7000:c00:3a00:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8d00e3d656fsm543904185a.17.2026.03.27.09.41.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2026 09:41:09 -0700 (PDT) Date: Fri, 27 Mar 2026 12:41:06 -0400 From: Johannes Weiner To: Baolin Wang Cc: akpm@linux-foundation.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, ljs@kernel.org, baohua@kernel.org, kasong@tencent.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU Message-ID: References: <3445af0f09e8ca945492e052e82594f8c4f2e2f6.1774606060.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3445af0f09e8ca945492e052e82594f8c4f2e2f6.1774606060.git.baolin.wang@linux.alibaba.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3837F40012 X-Stat-Signature: esajmc6ip3g4dqck4ocq9t1qdrfngf5w X-Rspam-User: X-HE-Tag: 1774629671-392478 X-HE-Meta: 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 wZwRmrSH 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 27, 2026 at 06:21:08PM +0800, Baolin Wang wrote: > The balance_dirty_pages() won't do the dirty folios throttling on cgroupv1. > See commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writeback > on traditional hierarchies"). > > Moreover, after commit 6b0dfabb3555 ("fs: Remove aops->writepage"), we no > longer attempt to write back filesystem folios through reclaim. > > On large memory systems, the flusher may not be able to write back quickly > enough. Consequently, MGLRU will encounter many folios that are already > under writeback. Since we cannot reclaim these dirty folios, the system > may run out of memory and trigger the OOM killer. > > Hence, for cgroup v1, let's throttle reclaim after waking up the flusher, > which is similar to commit 81a70c21d917 ("mm/cgroup/reclaim: fix dirty > pages throttling on cgroup v1"), to avoid unnecessary OOM. This fix for cgroup1 makes sense to me. For cgroup2, MGLRU shares the shrink_node() reclaim throttling. Acked-by: Johannes Weiner The remaining notable difference is global reclaim. I don't see any equivalent throttling in the lru_gen_shrink_node() path. What prevents premature OOMs at the system level?