linux-kernel - Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow writeback during memcg reclaim

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aUENEydFvVvxZK8r@infradead.org>
Date: Mon, 15 Dec 2025 23:41:07 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>,
	Deepanshu Kartikey <kartikey406@...il.com>,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: retiring laptop_mode? was Re: [PATCH] mm: vmscan: always allow
 writeback during memcg reclaim

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.

> 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.

Otherwise this looks good to me.