[PATCH v2 1/1] x86: Lower non-temporal copy threshold for Hygon

[H.J. Lu]

On Sat, May 9, 2026 at 3:58 PM Jiamei Xie <xiejiamei@hygon.cn> wrote:
>
> From: xiejiamei <xiejiamei@hygon.cn>
>
> Benchmarks on Hygon processors show that the default non-temporal
> threshold is higher than ideal for large copy workloads.  As a result,
> memcpy and memmove may continue to use the temporal copy path for
> longer than is beneficial, increasing cache pollution and reducing
> throughput for large copies.
>
> Lower the copy non-temporal threshold to 3/8 of the shared cache size
> per thread on Hygon.  This allows the non-temporal copy path to be
> selected earlier while leaving the memset non-temporal threshold
> unchanged.
>
> Signed-off-by: xiejiamei <xiejiamei@hygon.cn>
> ---
>  sysdeps/x86/dl-cacheinfo.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> index b6e17b0e32..c6cc36d363 100644
> --- a/sysdeps/x86/dl-cacheinfo.h
> +++ b/sysdeps/x86/dl-cacheinfo.h
> @@ -1248,6 +1248,14 @@ dl_init_cacheinfo (struct cpu_features *cpu_features)
>    if (tunable_size > minimum_non_temporal_threshold
>        && tunable_size <= maximum_non_temporal_threshold)
>      non_temporal_threshold = tunable_size;
> +  else if (cpu_features->basic.kind == arch_kind_hygon)
> +    {
> +      /* Hygon benefits from entering the non-temporal copy path earlier.
> +         Use 3/8 of the shared cache size per thread for memcpy and
> +         memmove.  The memset threshold has already been initialized
> +         above and is intentionally left unchanged.  */
> +      non_temporal_threshold = shared_per_thread * 3 / 8;
> +    }
>
>    tunable_size = TUNABLE_GET (x86_memset_non_temporal_threshold, long int, NULL);
>    if (tunable_size > minimum_non_temporal_threshold
> --
> 2.43.0
>
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.