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Fri, 15 Dec 2023 08:50:10 +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 bANZM0ITfGWCQwAAD6G6ig (envelope-from ); Fri, 15 Dec 2023 08:50:10 +0000 Date: Fri, 15 Dec 2023 09:50:04 +0100 From: Michal Hocko To: Dan Schatzberg Cc: Johannes Weiner , Roman Gushchin , Yosry Ahmed , Huan Yang , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Tejun Heo , Zefan Li , Jonathan Corbet , Shakeel Butt , Muchun Song , Andrew Morton , David Hildenbrand , Matthew Wilcox , Kefeng Wang , Yue Zhao , Hugh Dickins Subject: Re: [PATCH V4 2/2] mm: add swapiness= arg to memory.reclaim Message-ID: References: <20231213013807.897742-1-schatzberg.dan@gmail.com> <20231213013807.897742-3-schatzberg.dan@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: D7688100017 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 6rma4bm3ej4zipgmoguuzkztgry7kbhh X-HE-Tag: 1702630212-758992 X-HE-Meta: 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 QwyU4dqW 7lCqAhap4ry6KiDkT1YJzKKK/ttx1vTHmmnByvNATMsncq1MauYdK9CmNaOtv18TL0Aljzv8dONNSLKyhafPHrVDCgruY+GvCb1ui0H3p0wuVzGVQ7iiRf0nQqMxk/5GAno7/mPf7I7xkZRBZtoejs/gr1fwLznJOEXr6AIB4E/tlB1zpXAC780vu1a2PrkDQoUn3N8B5HaZ3qsBW4xtINSo6BQQ65WtY3eZdSYxMHsLkMcAvaTsm1Q3j6Thh99c/2IjRoWQ0Qo1QUqGJm9K0qria57G+iN7ockEN 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 Thu 14-12-23 13:22:29, Dan Schatzberg wrote: > On Thu, Dec 14, 2023 at 09:38:55AM +0100, Michal Hocko wrote: [...] > > While the review can point those out it is quite easy to break and you > > will only learn about that very indirectly. I think it would be easier > > to review and maintain if you go with a pointer that would fallback to > > mem_cgroup_swappiness() if NULL which will be the case for every > > existing reclaimer except memory.reclaim with swappiness value. > > I agree. My initial implementation used a pointer for this > reason. I'll switch this back. Just to be clear - I still need to > initialize scan_control.swappiness in all these other places right? No. They will just get initialized to 0. All you need to make sure is that the swappiness is used consistently. I would propose something like scan_control_swappiness() (or sc_swappiness) which would actually do if (sc->swappiness) return sc->swappiness; return mem_cgroup_swappiness(sc->target_mem_cgroup); and then make sure that mem_cgroup_swappiness is never used directly. -- Michal Hocko SUSE Labs