[PATCH v4 05/12] ARM: vfp: Record VFP bounces as perf emulation faults

[Linus Walleij]

On Mon, Mar 20, 2023 at 2:19 PM Ard Biesheuvel <ardb at kernel.org> wrote:

> VFP 'bouncing' occurs when the VFP unit cannot complete the execution of
> a VFP instruction, either because it is not implemented at all, or
> because the values of the arguments are out of range for the hardware
> implementation, and the software needs to step in to complete the
> operation.
>
> To give some insight in how much certain programs rely on this bouncing,
> record the emulation of a VFP instruction in perf's emulation-faults
> counter.
>
> This can be used like so
>
>   perf stat -e emulation-faults ./testfloat -all2
>
> and the output will be something like
>
>  Performance counter stats for './testfloat -all2':
>
>            259,277      emulation-faults:u
>
>        6.846432176 seconds time elapsed
>
> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>

Oh that's really useful.
Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij