linux-kernel - Re: [PATCH] mm/vmscan.c: drop_slab

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Date:   Tue, 6 Apr 2021 13:39:00 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Neil Sun <neilsun@...ify.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmscan.c: drop_slab_node with task's memcg

On Tue 06-04-21 19:30:22, Neil Sun wrote:
> On 2021/4/6 15:21, Michal Hocko wrote:
> > 
> > You are changing semantic of the existing user interface. This knob has
> > never been memcg aware and it is supposed to have a global impact. I do
> > not think we can simply change that without some users being surprised
> > or even breaking them.
> 
> Yes, do you think add new interface to sysfs is a good way? such as
> /sys/fs/cgroup/memory/lxc/i-vbe1u8o7/memory.kmem.drop_caches

There were other attempts to add a memcg specific alternative to
drop_caches. A lack of a strong usecase has been a reason that no such
attempt has been merged until now. drop_caches is a problematic
interface because it is really coarse and people have learned to (ab)use
it to workaround problem rather than fix them properly.

What is your usecase?
-- 
Michal Hocko
SUSE Labs