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Fri, 17 Apr 2026 10:35:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2V2EFNoM4mlTPQAAD6G6ig (envelope-from ); Fri, 17 Apr 2026 10:35:06 +0000 Date: Fri, 17 Apr 2026 11:35:04 +0100 From: Pedro Falcato To: Shakeel Butt Cc: Matt Fleming , Andrew Morton , Christoph Hellwig , Jens Axboe , Sergey Senozhatsky , Roman Gushchin , Minchan Kim , kernel-team@cloudflare.com, Matt Fleming , Johannes Weiner , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , Axel Rasmussen , Yuanchu Xie , Wei Xu , David Hildenbrand , Qi Zheng , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Require LRU reclaim progress before retrying direct reclaim Message-ID: References: <20260410101550.2930139-1-matt@readmodwrite.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: F39B880002 X-Stat-Signature: bsgp949ae8s914n6tk46s6eat6a3na5z X-Rspam-User: X-HE-Tag: 1776422113-979768 X-HE-Meta: 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 R6txwWMq vVTdDMtMxVg+bPu7LxlO/GRePIRbPVbHyv9szticFBhHoMkbd4aUUXKtIwmITiaP1n1l400UWASRW3YXiySyfaP2orYLy/+r0Rc3r86Mb2G0OTBly9SvEd/ZSic5xB+ittGVtiEzxkZQf/+Seoc7YMNTYGunm4uuGcVPDS3B0LC6DBr6Wl5+SpT8nlH19dOvdxJPfJZgbqZsCalR+oAEejCiecRg8DviKuJ6hfDo/tS2E49aizWdFuOqzcRU6L5objwuLOUVwjIau8vImI1ENNJjUAe8jk6aawHQo4TNS+idM/fk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 16, 2026 at 02:49:28PM -0700, Shakeel Butt wrote: > On Thu, Apr 16, 2026 at 03:51:04PM +0100, Matt Fleming wrote: > > On Wed, Apr 15, 2026 at 03:57:25PM +0100, Pedro Falcato wrote: > [...] > > > > > My theory (from merely reading the patch, maybe I missed something) is that > > > a pathological case for this is a lot of folios added to the LRU in a row, > > > that are set referenced (or dirty). Say SWAP_CLUSTER_MAX * MAX_RECLAIM_RETRIES > > > - it will simply OOM too early. > > > > OK yeah I think I see the problem now: this heuristic applies the > > threshold against all reclaimable pages but that falls apart when doing > > SWAP_CLUSTER_MAX chunks of reclaim. > > I am not sure I understand the pathological case. Yes SWAP_CLUSTER_MAX is > requested amount of pages to reclaim but the kernel can potentially scan full > memory twice to reclaim that much amount. Though those reclaimed pages can get > stolen but that can still happen today before this patch. I see, yes, you are totally correct. Had a look at the vmscan code again and just realized I had missed some details. Matt, please disregard :) -- Pedro