linux-kernel - Re: [Regression] mqueue performance degradation after "The new cgroup slab memory controller" patchset.

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Message-ID: <CALvZod6FGQyuubJ0tAjvBHrhc7r-wFsaz7so74Yk_Fd8x3yLOQ@mail.gmail.com>
Date:   Mon, 5 Dec 2022 08:06:19 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     "Luther, Sven" <Sven.Luther@...driver.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Roman Gushchin <guro@...com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "kernel-team@...com" <kernel-team@...com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Muchun Song <songmuchun@...edance.com>,
        Waiman Long <longman@...hat.com>,
        Alexey Gladkov <legion@...nel.org>,
        "Bonn, Jonas" <Jonas.Bonn@...driver.com>
Subject: Re: [Regression] mqueue performance degradation after "The new cgroup
 slab memory controller" patchset.

Hi Sven,

On Mon, Dec 5, 2022 at 6:56 AM Luther, Sven <Sven.Luther@...driver.com> wrote:
>
> #regzbot ^introduced 10befea91b61c4e2c2d1df06a2e978d182fcf792
>
> We are making heavy use of mqueues, and noticed a degradation of performance between 4.18 & 5.10 linux kernels.
>
> After a gross per-version tracing, we did kernel bisection between 5.8 and 5.9
> and traced the issue to a 10 patches (of which 9 where skipped as they didn't boot) between:
>
>
> commit 10befea91b61c4e2c2d1df06a2e978d182fcf792 (HEAD, refs/bisect/bad)
> Author: Roman Gushchin <guro@...com>
> Date:   Thu Aug 6 23:21:27 2020 -0700
>
>     mm: memcg/slab: use a single set of kmem_caches for all allocations
>
> and:
>
> commit 286e04b8ed7a04279ae277f0f024430246ea5eec (refs/bisect/good-286e04b8ed7a04279ae277f0f024430246ea5eec)
> Author: Roman Gushchin <guro@...com>
> Date:   Thu Aug 6 23:20:52 2020 -0700
>
>     mm: memcg/slab: allocate obj_cgroups for non-root slab pages
>
> All of them are part of the "The new cgroup slab memory controller" patchset:
>
>   https://lore.kernel.org/all/20200623174037.3951353-18-guro@fb.com/T/
>
> from Roman Gushchin, which moves the accounting for page level to the object level.
>
> Measurements where done using the a test programmtest, which measures mix/average/max time mqueue_send/mqueue_rcv,
> and average for getppid, both measured over 100 000 runs. Results are shown in the following table
>
> +----------+--------------------------+-------------------------+----------------+
> | kernel   |    mqueue_rcv (ns)       | mqueue_send (ns)        |    getppid     |
> | version  | min avg  max   variation | min avg max   variation | (ns) variation |
> +----------+--------------------------+-------------------------+----------------+
> | 4.18.45  | 351 382 17533     base   | 383 410 13178     base  | 149      base  |
> | 5.8-good | 380 392  7156   -2,55%   | 376 384  6225    6,77%  | 169   -11,83%  |
> | 5.8-bad  | 524 530  5310  -27,92%   | 512 519  8775  -21,00%  | 169   -11,83%  |
> | 5.10     | 520 533  4078  -28,33%   | 518 534  8108  -23,22%  | 167   -10,78%  |
> | 5.15     | 431 444  8440  -13,96%   | 425 437  6170   -6,18%  | 171   -12,87%  |
> | 6.03     | 474 614  3881  -37,79%   | 482 693   931  -40,84%  | 171   -12,87%  |
> +----------+--------------------------+-------------------------+-----------------
>

Is the last kernel 6.0.3? Also we know there is performance impact of
per-object kmem accounting. Can you try the latest i.e. 6.1-rc8? There
are a couple of memcg charging optimization patches merged in this
window.