[PATCH v2] arm64: clear_page[s] using memset

[Linus Walleij]

On Tue, Oct 13, 2026 at 3:04 PM Catalin Marinas <catalin.marinas at arm.com> wrote:

> Trying to make sense of the above. So based on -next of 22nd of
> September, the table means:
>
> vanilla         - next/master on that day (current clear_page())
> patch           - memset()-based clear_page() patch (Linus's patch)
> stnp            - vanilla clear_page() without DC ZVA
> patch_stp       - memset()-based clear_page() patch without DC ZVA
>
> I assume the vanilla vs patch columns are just noise. Well, there's a
> -1.17% regression (not flagged) on Ampere but what's the standard
> deviation for this column? Similarly for the -1.15% on the AWS patch_stp
> test (vs stnp in the same test, it's no worse).
>
> Vanilla vs stnp shows a regression on Ampere, however that's expected as
> we no longer do the DC ZVA. Interestingly, the patch_stp result doesn't have
> this regression, so I reckon DC ZVA behaves mostly in line with STP on
> this hardware.
>
> Basically I was looking for the stnp vs patch_stp results. If I read it
> correctly, there's no significant change going from non-temporal to
> temporal stores (and a small improvement for Ampere). Assuming future
> FEAT_MOPS will have similar behaviour, moving clear_page() to memset()
> shouldn't cause any regressions. Before FEAT_MOPS, we'll use DC ZVA here
> anyway.

That almost sounds like an Acked-by if Usama can confirm your
assumptions above!

Yours,
Linus Walleij