linux-kernel - Re: [PATCH RFC 4/4] mitigations: Add flock cache accounting to 'mitigations=off'

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Date: Thu, 18 Jan 2024 10:04:29 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, 
	Jeff Layton <jlayton@...nel.org>, Chuck Lever <chuck.lever@...cle.com>, 
	Shakeel Butt <shakeelb@...gle.com>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org, 
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>, 
	Vasily Averin <vasily.averin@...ux.dev>, Waiman Long <longman@...hat.com>, 
	Muchun Song <muchun.song@...ux.dev>, Jiri Kosina <jikos@...nel.org>, cgroups@...r.kernel.org, 
	linux-mm@...ck.org
Subject: Re: [PATCH RFC 4/4] mitigations: Add flock cache accounting to
 'mitigations=off'

On Wed, Jan 17, 2024 at 08:14:46AM -0800, Josh Poimboeuf <jpoimboe@...nel.org> wrote:
> Allow flock cache accounting to be disabled with 'mitigations=off', as
> it fits the profile for that option: trusted user space combined with a
> performance-impacting mitigation.

Note that some other kernel objects that don't have any other tight
limit are already charged too (but their charging likely did not stand
out in any performance regression tests).
In the situation you describe, users can already pass
`cgroup.memory=nokmem` and get rid of charging overhead in general.

IOW, if flock objects are charged, there already is a boot option to
turn off such behavior.

Regards,
Michal

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