linux-kernel - Re: [PATCH] mm, memcg: Add a memcg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <a33fba37-ef61-8179-9994-df7e04cc5866@redhat.com>
Date:   Wed, 19 Jun 2019 11:47:40 -0400
From:   Waiman Long <longman@...hat.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>
Subject: Re: [PATCH] mm, memcg: Add a memcg_slabinfo debugfs file

On 6/19/19 11:35 AM, Shakeel Butt wrote:
> On Wed, Jun 19, 2019 at 8:30 AM Waiman Long <longman@...hat.com> wrote:
>> On 6/19/19 11:18 AM, Shakeel Butt wrote:
>>> On Wed, Jun 19, 2019 at 7:46 AM Waiman Long <longman@...hat.com> wrote:
>>>> There are concerns about memory leaks from extensive use of memory
>>>> cgroups as each memory cgroup creates its own set of kmem caches. There
>>>> is a possiblity that the memcg kmem caches may remain even after the
>>>> memory cgroup removal. Therefore, it will be useful to show how many
>>>> memcg caches are present for each of the kmem caches.
>>>>
>>>> This patch introduces a new <debugfs>/memcg_slabinfo file which is
>>>> somewhat similar to /proc/slabinfo in format, but lists only slabs that
>>>> are in memcg kmem caches. Information available in /proc/slabinfo are
>>>> not repeated in memcg_slabinfo.
>>>>
>>> At Google, we have an interface /proc/slabinfo_full which shows each
>>> kmem cache (root and memcg) on a separate line i.e. no accumulation.
>>> This interface has helped us a lot for debugging zombies and memory
>>> leaks. The name of the memcg kmem caches include the memcg name, css
>>> id and "dead" for offlined memcgs. I think these extra information is
>>> much more useful for debugging. What do you think?
>>>
>>> Shakeel
>> Yes, I think that can be a good idea. My only concern is that it can be
>> very verbose. Will work on a v2 patch.
>>
> Yes, it is very verbose but it is only for debugging and normal users
> should not be (continuously) reading that interface.

I am not against it. It is just an observation. I still think we can
skip kmem caches that don't have any child memcg caches as the
information is in slabinfo already.

Cheers,
Longman