linux-kernel - Re: [PATCH v6 12/19] mm: memcg/slab: use a single set of kmem

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Message-ID: <CALvZod6xjB6kioQ8uRT3VoMQYmT-b4Z-wue0CPim3J8u12KZtA@mail.gmail.com>
Date:   Mon, 22 Jun 2020 09:56:41 -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 12/19] mm: memcg/slab: use a single set of kmem_caches
 for all accounted allocations

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@...com> wrote:
>
> This is fairly big but mostly red patch, which makes all accounted
> slab allocations use a single set of kmem_caches instead of
> creating a separate set for each memory cgroup.
>
> Because the number of non-root kmem_caches is now capped by the number
> of root kmem_caches, there is no need to shrink or destroy them
> prematurely. They can be perfectly destroyed together with their
> root counterparts. This allows to dramatically simplify the
> management of non-root kmem_caches and delete a ton of code.
>
> This patch performs the following changes:
> 1) introduces memcg_params.memcg_cache pointer to represent the
>    kmem_cache which will be used for all non-root allocations
> 2) reuses the existing memcg kmem_cache creation mechanism
>    to create memcg kmem_cache on the first allocation attempt
> 3) memcg kmem_caches are named <kmemcache_name>-memcg,
>    e.g. dentry-memcg
> 4) simplifies memcg_kmem_get_cache() to just return memcg kmem_cache
>    or schedule it's creation and return the root cache
> 5) removes almost all non-root kmem_cache management code
>    (separate refcounter, reparenting, shrinking, etc)
> 6) makes slab debugfs to display root_mem_cgroup css id and never
>    show :dead and :deact flags in the memcg_slabinfo attribute.
>
> Following patches in the series will simplify the kmem_cache creation.
>
> Signed-off-by: Roman Gushchin <guro@...com>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

This is a very satisfying patch.

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>