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From: Shakeel Butt To: Jiayuan Chen Cc: linux-mm@kvack.org, Andrew Morton , Johannes Weiner , David Hildenbrand , Michal Hocko , Qi Zheng , Lorenzo Stoakes , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/vmscan: skip increasing kswapd_failures when reclaim was boosted Message-ID: <7rx23a4moclrdb6csumf2g3kfp7rgy7przq6lsknwumeb35x2c@jhrmjdcfhzcf> References: <20251024022711.382238-1-jiayuan.chen@linux.dev> <59f26b5b0c49f8d0f3bdb33f99d69dd3d442ed60@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <59f26b5b0c49f8d0f3bdb33f99d69dd3d442ed60@linux.dev> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 5uf8t9r8zkfggpmwdfh1jr31fadd5opp X-Rspam-User: X-Rspamd-Queue-Id: BBBF520005 X-Rspamd-Server: rspam01 X-HE-Tag: 1763077274-952249 X-HE-Meta: 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 OhugfxdC pxvt+xbBwEbugRgvb4DNqPSq50QBYe1HHGRB1ZcdER3FMxBdOfVieww0Ev1xl3QQ3plx+Ixc833y5Ni+FsJn57xgzch92zf40ZcctLdPs/VOwcdluQH1UMVrYrrldjXkfYX6eY0X88MuH/doeDc+p7hh2HEHydEcoiVnu+7NJKpFVJQ2qw1b4EHYNcgpQSwRrtX9TFJjy4j6bPhIf2bDgwd5c0LjnsBmbGcGtQx2VHN01YSdeaKQJttfclxUF5nM6qgnO X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Nov 12, 2025 at 02:21:37AM +0000, Jiayuan Chen wrote: > 2025/11/8 09:11, "Shakeel Butt" wrote: [...] > > If this issue (high protection causing kswap > > failures) happen on non-boosted case, I am not sure what should be right > > behavior i.e. allocators doing direct reclaim potentially below low > > protection or allowing kswapd to reclaim below low. For min, it is very > > clear that direct reclaimer has to reclaim as they may have to trigger > > oom-kill. For low protection, I am not sure. > > > > We have also encountered this issue in non-boosted scenarios. For instance, when > we disabled swap (meaning only file pages are reclaimed, not anonymous pages), it > indeed occurred even without memory.low configured, especially when anonymous pages > constituted the majority. Basically whenever the amount of reclaimable memory is low (i.e. in the range where it is very hard to satisfy the watermarks), this issue can happen. 'This' as in kswapd failures. This functionality was added to detect such scenarios where kswapd hogs a CPU doing nothing. The memory.low adds a twist that we can allow kswapd to go after but let's punt on that for now and go after the clear and easy issue i.e. kswapd failures due to boosted watermarks.