Re: [PATCH v10 6/8] x86/clear_page: Introduce clear_pages()

[David Hildenbrand (Red Hat)]

On 12/15/25 21:49, Ankur Arora wrote:
> Performance when clearing with string instructions (x86-64-stosq and
> similar) can vary significantly based on the chunk-size used.
>
>    $ perf bench mem memset -k 4KB -s 4GB -f x86-64-stosq
>    # Running 'mem/memset' benchmark:
>    # function 'x86-64-stosq' (movsq-based memset() in arch/x86/lib/memset_64.S)
>    # Copying 4GB bytes ...
>
>        13.748208 GB/sec
>
>    $ perf bench mem memset -k 2MB -s 4GB -f x86-64-stosq
>    # Running 'mem/memset' benchmark:
>    # function 'x86-64-stosq' (movsq-based memset() in
>    # arch/x86/lib/memset_64.S)
>    # Copying 4GB bytes ...
>
>        15.067900 GB/sec
>
>    $ perf bench mem memset -k 1GB -s 4GB -f x86-64-stosq
>    # Running 'mem/memset' benchmark:
>    # function 'x86-64-stosq' (movsq-based memset() in arch/x86/lib/memset_64.S)
>    # Copying 4GB bytes ...
>
>        38.104311 GB/sec
>
> (Both on AMD Milan.)
>
> With a change in chunk-size from 4KB to 1GB, we see the performance go
> from 13.7 GB/sec to 38.1 GB/sec. For the chunk-size of 2MB the change isn't
> quite as drastic but it is worth adding a clear_page() variant that can
> handle contiguous page-extents.
>
> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
> Tested-by: Raghavendra K T <raghavendra.kt@xxxxxxx>

Nothing jumped at me.

Reviewed-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>

--
Cheers

David