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

[Johannes Weiner]

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!