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[109.81.92.149]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432449346c9sm641020f8f.5.2025.12.17.11.34.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Dec 2025 11:34:43 -0800 (PST) Date: Wed, 17 Dec 2025 20:34:42 +0100 From: Michal Hocko To: Johannes Weiner Cc: Christoph Hellwig , Jens Axboe , Deepanshu Kartikey , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow writeback during memcg reclaim Message-ID: References: <20251213083639.364539-1-kartikey406@gmail.com> <20251215041200.GB905277@cmpxchg.org> <20251215200838.GC905277@cmpxchg.org> <20251216185201.GH905277@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251216185201.GH905277@cmpxchg.org> X-Rspam-User: X-Rspamd-Queue-Id: 13345A0009 X-Rspamd-Server: rspam10 X-Stat-Signature: rcafoocdgpoy9bcfekc99nf9c3so51an X-HE-Tag: 1766000085-707087 X-HE-Meta: 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 b7u/FKjZ 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 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 Tue 16-12-25 13:52:01, Johannes Weiner wrote: > On Mon, Dec 15, 2025 at 11:41:07PM -0800, Christoph Hellwig wrote: > > On Mon, Dec 15, 2025 at 03:08:38PM -0500, Johannes Weiner wrote: > > > Debated whether to add some sort of deprecation sysctl handler, but at > > > least systemd-sysctl just prints a warning and still applies other > > > settings from the same config file. > > > > In general dropping sysctl will break things. So I think we'll need > > a stub, at which point it might as well warn for a while. > > Fair enough, I added that. > > Jens, that change seemed small enough that I carried your Ack, but > please let me know if you feel otherwise ;) > > > > Laptop mode was introduced to save battery, by delaying and > > > consolidating writes and maximize the time rotating hard drives > > > wouldn't have to spin. Needless to say, this is a scenario of the > > > (in)glorious past. > > > > Maybe expand on this a bit by mentioning that reclaim now never does > > file system writeback, and fs writeback is already very lumpy by > > design. And of cours that hard disk with their high spinup latency > > and extra power draw are a thing of the past in laptops or other mobile > > devices. > > Sounds good. Can you take a look at the new version below? > > Andrew, absent any further objections, would you be able to take this > through the -mm tree? > > Thanks! > > >From 087f10b8046864f71ebc3a3f3316b097932cbded Mon Sep 17 00:00:00 2001 > From: Johannes Weiner > Date: Mon, 15 Dec 2025 12:57:53 -0500 > Subject: [PATCH] mm/block/fs: remove laptop_mode > > Laptop mode was introduced to save battery, by delaying and > consolidating writes and thereby maximize the time rotating hard > drives wouldn't have to spin. > > Luckily, rotating hard drives, with their high spin-up times and power > draw, are a thing of the past for battery-powered devices. Reclaim has > also since changed to not write single filesystem pages anymore, and > regular filesystem writeback is lumpy by design. > > The juice doesn't appear worth the squeeze anymore. The footprint of > the feature is small, but nevertheless it's a complicating factor in > mm, block, filesystems. Developers don't think about it, and it likely > hasn't been tested with new reclaim and writeback changes in years. > > Let's sunset it. Keep the sysctl with a deprecation warning around for > a few more cycles, but remove all functionality behind it. > > Suggested-by: Christoph Hellwig > Message-ID: > Acked-by: Jens Axboe > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Thanks! -- Michal Hocko SUSE Labs