linux-kernel - Re: [PATCH] memcg, kmem: further deprecate kmem.limit_in

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Message-ID: <20201118194620.GD186396@carbon.dhcp.thefacebook.com>
Date:   Wed, 18 Nov 2020 11:46:20 -0800
From:   Roman Gushchin <guro@...com>
To:     Shakeel Butt <shakeelb@...gle.com>
CC:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] memcg, kmem: further deprecate kmem.limit_in_bytes

On Wed, Nov 18, 2020 at 09:57:26AM -0800, Shakeel Butt wrote:
> The deprecation process of kmem.limit_in_bytes started with the commit
> 0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also
> explains in detail the motivation behind the deprecation. To summarize,
> it is the unexpected behavior on hitting the kmem limit. This patch
> moves the deprecation process to the next stage by disallowing to set
> the kmem limit. In future we might just remove the kmem.limit_in_bytes
> file completely.
> 
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

The first stage was done over a year ago, so if there were no complains
it feels like it's a good time to move forward.

Acked-by: Roman Gushchin <guro@...com>

The only question I have is if it's better to return -EINVAL or -ENOTSUPP.
The latter option could be more convenient for userspace, because it will
be clear that the kernel is not supporting the functionality, rather than
the passed value is incorrect (e.g. if the value is read from a config, provided
by a user). I'm not sure though, just an idea.

Thanks!