Re: [PATCH v4] Documentation: Add document for false sharing

[Jonathan Corbet]

Feng Tang <feng.tang@xxxxxxxxx> writes:

> When doing performance tuning or debugging performance regressions,
> more and more cases are found to be related to false sharing [1][2][3],
> and the situation can be worse for newer platforms with hundreds of
> CPUs. There are already many commits in current kernel specially
> for mitigating the performance degradation due to false sharing.
>
> False sharing could harm the performance silently without being
> noticed, due to reasons like:
> * data members of a big data structure randomly sitting together
>   in one cache line
> * global data of small size are linked compactly together
>
> So it's better to make a simple document about the normal pattern
> of false sharing, basic ways to mitigate it and call out to
> developers to pay attention during code-writing.
>
> [ Many thanks to Dave Hansen, Ying Huang, Tim Chen, Julie Du and
>   Yu Chen for their contributions ]
>
> [1]. https://lore.kernel.org/lkml/20220619150456.GB34471@xsang-OptiPlex-9020/
> [2]. https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/
> [3]. https://lore.kernel.org/lkml/20230307125538.818862491@xxxxxxxxxxxxx/
>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>

Applied, thanks.

jon