linux-kernel - Re: [PATCH] memcg: Add kmem.slabinfo to v2 for debugging purpose

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Message-ID: <78c5ba55-b755-1997-edcc-9ee03a3f3300@redhat.com>
Date:   Thu, 27 Jun 2019 09:47:40 -0400
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH] memcg: Add kmem.slabinfo to v2 for debugging purpose

On 6/26/19 6:25 PM, Andrew Morton wrote:
> On Wed, 26 Jun 2019 12:56:14 -0400 Waiman Long <longman@...hat.com> wrote:
>
>> With memory cgroup v1, there is a kmem.slabinfo file that can be
>> used to view what slabs are allocated to the memory cgroup. There
>> is currently no such equivalent in memory cgroup v2. This file can
>> be useful for debugging purpose.
>>
>> This patch adds an equivalent kmem.slabinfo to v2 with the caveat that
>> this file will only show up as ".__DEBUG__.memory.kmem.slabinfo" when the
>> "cgroup_debug" parameter is specified in the kernel boot command line.
>> This is to avoid cluttering the cgroup v2 interface with files that
>> are seldom used by end users.
>>
>> ...
>>
>> mm/memcontrol.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
> A change to the kernel's user interface triggers a change to the
> kernel's user interface documentation.  This should be automatic by
> now :(
>
>
We don't usually document debugging only files as they are subject to
change with no stability guarantee. That is the point of marking it for
debugging instead of a regular file that we need to support forever.

Cheers,
Longman