linux-kernel - Re: [PATCH v6 15/19] mm: memcg/slab: deprecate slab_root

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Message-ID: <CALvZod6drr_eQS7iv9toFJcz9xSL5qxdfBw09D4NxUwq2aG55A@mail.gmail.com>
Date:   Mon, 22 Jun 2020 10:36:21 -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 15/19] mm: memcg/slab: deprecate slab_root_caches

On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@...com> wrote:
>
> Currently there are two lists of kmem_caches:
> 1) slab_caches, which contains all kmem_caches,
> 2) slab_root_caches, which contains only root kmem_caches.
>
> And there is some preprocessor magic to have a single list
> if CONFIG_MEMCG_KMEM isn't enabled.
>
> It was required earlier because the number of non-root kmem_caches
> was proportional to the number of memory cgroups and could reach
> really big values. Now, when it cannot exceed the number of root
> kmem_caches, there is really no reason to maintain two lists.
>
> We never iterate over the slab_root_caches list on any hot paths,
> so it's perfectly fine to iterate over slab_caches and filter out
> non-root kmem_caches.
>
> It allows to remove a lot of config-dependent code and two pointers
> from the kmem_cache structure.
>
> Signed-off-by: Roman Gushchin <guro@...com>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

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