linux-kernel - Re: [PATCH v6 10/19] mm: memcg/slab: deprecate memory.kmem.slabinfo

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Date:   Mon, 22 Jun 2020 10:12:46 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Roman Gushchin <guro@...com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Linux MM <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Kernel Team <kernel-team@...com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 10/19] mm: memcg/slab: deprecate memory.kmem.slabinfo

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@...com> wrote:
>
> Deprecate memory.kmem.slabinfo.
>
> An empty file will be presented if corresponding config options are
> enabled.
>
> The interface is implementation dependent, isn't present in cgroup v2,
> and is generally useful only for core mm debugging purposes. In other
> words, it doesn't provide any value for the absolute majority of users.
>
> A drgn-based replacement can be found in tools/cgroup/slabinfo.py .
> It does support cgroup v1 and v2, mimics memory.kmem.slabinfo output
> and also allows to get any additional information without a need
> to recompile the kernel.
>
> If a drgn-based solution is too slow for a task, a bpf-based tracing
> tool can be used, which can easily keep track of all slab allocations
> belonging to a memory cgroup.
>
> Signed-off-by: Roman Gushchin <guro@...com>
> Acked-by: Johannes Weiner <hannes@...xchg.org>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Hi Roman,

I am not against removing the memory.kmem.slabinfo interface but I
would like to have an alternative solution more accessible than
tools/cgroup/slabinfo.py.

In our case, we don't have ssh access and if we need something for
debugging, it is much more preferable to provide a file to read to
SREs. After the review, that file will be added to a whitelist and
then we can directly read that file through automated tools without
approval for each request.

I am just wondering if a file interface can be provided for whatever
tools/cgroup/slabinfo.py is providing.

Shakeel