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

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Message-ID: <2ed0737c-2b2c-4f99-858f-2a4bc4a477ae@kernel.dk>
Date: Mon, 15 Dec 2025 09:33:43 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Christoph Hellwig <hch@...radead.org>,
 Johannes Weiner <hannes@...xchg.org>
Cc: 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 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