Re: [PATCH v2 3/5] mm: memcg: make stats flushing threshold per-memcg

[Shakeel Butt]

On Fri, Oct 20, 2023 at 9:18 AM kernel test robot <oliver.sang@xxxxxxxxx> wrote:
>
>
>
> Hello,
>
> kernel test robot noticed a -25.8% regression of will-it-scale.per_thread_ops on:
>
>
> commit: 51d74c18a9c61e7ee33bc90b522dd7f6e5b80bb5 ("[PATCH v2 3/5] mm: memcg: make stats flushing threshold per-memcg")
> url: https://github.com/intel-lab-lkp/linux/commits/Yosry-Ahmed/mm-memcg-change-flush_next_time-to-flush_last_time/20231010-112257
> base: https://git.kernel.org/cgit/linux/kernel/git/akpm/mm.git mm-everything
> patch link: https://lore.kernel.org/all/20231010032117.1577496-4-yosryahmed@xxxxxxxxxx/
> patch subject: [PATCH v2 3/5] mm: memcg: make stats flushing threshold per-memcg
>
> testcase: will-it-scale
> test machine: 104 threads 2 sockets (Skylake) with 192G memory
> parameters:
>
>         nr_task: 100%
>         mode: thread
>         test: fallocate1
>         cpufreq_governor: performance
>
>
> In addition to that, the commit also has significant impact on the following tests:
>
> +------------------+---------------------------------------------------------------+
> | testcase: change | will-it-scale: will-it-scale.per_thread_ops -30.0% regression |
> | test machine     | 104 threads 2 sockets (Skylake) with 192G memory              |
> | test parameters  | cpufreq_governor=performance                                  |
> |                  | mode=thread                                                   |
> |                  | nr_task=50%                                                   |
> |                  | test=fallocate1                                               |
> +------------------+---------------------------------------------------------------+
>

Yosry, I don't think 25% to 30% regression can be ignored. Unless
there is a quick fix, IMO this series should be skipped for the
upcoming kernel open window.