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

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Message-ID: <20190627142024.GW657710@devbig004.ftw2.facebook.com>
Date:   Thu, 27 Jun 2019 07:20:24 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH] memcg: Add kmem.slabinfo to v2 for debugging purpose

Hello, Waiman.

On Wed, Jun 26, 2019 at 12:56:14PM -0400, Waiman Long 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.

Can you please take a look at drgn?

  https://github.com/osandov/drgn

Baking in debug interface files always is limited and nasty and drgn
can get you way more flexible debugging / monitoring tool w/o having
to bake in anything into the kernel.  For an example, please take a
look at

  https://lore.kernel.org/bpf/20190614015620.1587672-10-tj@kernel.org/

Thanks.

-- 
tejun