linux-kernel - Re: [PATCH RFC 2/2] mm: kmem: add direct objcg pointer to task

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Message-ID: <20221222135044.GB20830@blackbody.suse.cz>
Date:   Thu, 22 Dec 2022 14:50:44 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 2/2] mm: kmem: add direct objcg pointer to task_struct

On Tue, Dec 20, 2022 at 10:27:45AM -0800, Roman Gushchin <roman.gushchin@...ux.dev> wrote:
> To charge a freshly allocated kernel object to a memory cgroup, the
> kernel needs to obtain an objcg pointer. Currently it does it
> indirectly by obtaining the memcg pointer first and then calling to
> __get_obj_cgroup_from_memcg().

Jinx [1].

You report additional 7% improvement with this patch (focused on
allocations only). I didn't see impressive numbers (different benchmark
in [1]), so it looked as a microoptimization without big benefit to me.

My 0.02€ to RFC,
Michal


[1] https://bugzilla.kernel.org/show_bug.cgi?id=216038#c5

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