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Mon, 15 Dec 2025 08:33:44 -0800 (PST) Message-ID: <2ed0737c-2b2c-4f99-858f-2a4bc4a477ae@kernel.dk> Date: Mon, 15 Dec 2025 09:33:43 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow writeback during memcg reclaim To: Christoph Hellwig , Johannes Weiner Cc: Deepanshu Kartikey , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org References: <20251213083639.364539-1-kartikey406@gmail.com> <20251215041200.GB905277@cmpxchg.org> Content-Language: en-US From: Jens Axboe In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 9krf5ad4ny65gc4cwsbskanbr4z6z4eh X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7D397160023 X-HE-Tag: 1765816426-291296 X-HE-Meta: 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 cpbg0ufn 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000035, 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 12/14/25 11:59 PM, Christoph Hellwig wrote: > On Sun, Dec 14, 2025 at 11:12:00PM -0500, Johannes Weiner wrote: >> That reasoning doesn't make sense to me. Reclaim is always in response >> to an allocation need. The laptop_mode idea applies to cgroup reclaim >> as much as any other reclaim. >> >> Now obviously all of this is pretty dated. Reclaim doesn't do >> filesystem writes anymore, and I'm not sure there are a whole lot of >> laptops with rotational drives left, either. Also I doubt anybody is >> still using zone_reclaim_mode (which is where the may_unmap is from). > > Yeah. I wonder if we should retire laptop_mode. It was a cute hack > back then, but it has it's ugly fingers in way to many places and > should be mostly obsolete by how writeback works these days. I'd be all for that. -- Jens Axboe