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From: Shakeel Butt 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-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7FA2140006 X-Stat-Signature: cxo8ukeyaf6kgrhcu1fxdcg99fshab8a X-HE-Tag: 1765927445-159055 X-HE-Meta: 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 Sne8zNBL f7TGmxgXUzWZzE0B80mPjOdLJsHtO2orfuiIMGXrEWI9GQky7zAB3xwxlZ8CgmaJbnlVQqrKYvs0qT2+THy84H/zWWoLrumMiq+A8R87V0/6uORtJu3WUeVAAaCqFiXcydVV0fMgI/OcdGtzsSBQGIi0IadGpCTa8ydx0+j5HPg/LQIr29m8g64e6CtkGFfrBZ3EuyKOz0w+Dr/LRDhKFsvlrueqwXZHTMvmF9aW2xZKrK/5WVPSdXMptv/RSsXGJ3TcLpl0ZZwtWoKoOU117vm18+1cIhL7XWIry3an5rmgH+fPMdtzhIwSbHXdjTPGGrDmD01avfvG28trhG5KK9/t/wrZVD4isPE66B7y0UToEDVe0jxctvx7/WV9BULW8hhy1Z5zOaktRa9bKLKy/fNq1aUx1l2ihc+eS 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, Dec 16, 2025 at 01:52:01PM -0500, Johannes Weiner wrote: [...] > > 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: Is there a need for above message ID? Why not put the whole lore link? > Acked-by: Jens Axboe > Signed-off-by: Johannes Weiner One nit below and other than that you can add: Reviewed-by: Shakeel Butt > --- a/include/uapi/linux/sysctl.h > +++ b/include/uapi/linux/sysctl.h > @@ -183,7 +183,7 @@ enum > VM_LOWMEM_RESERVE_RATIO=20,/* reservation ratio for lower memory zones */ > VM_MIN_FREE_KBYTES=21, /* Minimum free kilobytes to maintain */ > VM_MAX_MAP_COUNT=22, /* int: Maximum number of mmaps/address-space */ > - VM_LAPTOP_MODE=23, /* vm laptop mode */ > + There are 8 earlier enums here with names like VM_UNUSED* along with the information on what were they. Should we have something similar for this one? Something like: VM_UNUSED10=23, /* was vm laptop mode */