ACK/Cmnt: [SRU][jammy][PATCH 0/1] performance: address_space: add padding for i_map and i_mmap_rwsem to mitigate a false sharing

[Stefan Bader]

On 13.02.24 21:42, Philip Cox wrote:
> 
> BugLink: https://bugs.launchpad.net/bugs/2053069
> 
> SRU Justification:
> 
> [Impact]
> In high core count systems such as Intel Sapphire Rapids
> (with a 112C/224T count) this this change improvesgeekbench performance by
> ~5.3% due to moving the elements in the address_space struct.
> 
> [Fix]
> by moving i_mmap_rwsema, vma_interval_tree_remove is no longer in cacheline 0
> which improves the performance.
> 
> 
> [Test Plan]
> I've tested this change, as has Intel.  This change has also been upstreamed
> for some time.
> 
> [Where problems could occur]
> The risk for regression is fairly low, as we are just changing the layout
> of a stuct to change where members land in the cache.
> 
> --
> 
> Zhu, Lipeng (1):
>    fs/address_space: add alignment padding for i_map and i_mmap_rwsem to
>      mitigate a false sharing.
> 
>   include/linux/fs.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 

This patch is upstream as of v6.6 (the devel task of the bug report 
should be fix-released or invalid). However that brings up the question 
about Mantic/6.5. Should this not also be included there?

Acked-by: Stefan Bader <stefan.bader at canonical.com>
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