Applied. Thanks!
Alex
On Mon, Jul 3, 2023 at 7:16 PM Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
>
> Use local64_try_cmpxchg instead of local64_cmpxchg (*ptr, old, new) == old
> in amdgpu_perf_read. x86 CMPXCHG instruction returns success in ZF flag,
> so this change saves a compare after cmpxchg (and related move instruction
> in front of cmpxchg).
>
> Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
> fails. There is no need to re-read the value in the loop.
>
> No functional change intended.
>
> Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> Cc: "Christian König" <christian.koenig@xxxxxxx>
> Cc: "Pan, Xinhui" <Xinhui.Pan@xxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c
> index 71ee361d0972..6e91ea1de5aa 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pmu.c
> @@ -276,9 +276,8 @@ static void amdgpu_perf_read(struct perf_event *event)
> (!pe->adev->df.funcs->pmc_get_count))
> return;
>
> + prev = local64_read(&hwc->prev_count);
> do {
> - prev = local64_read(&hwc->prev_count);
> -
> switch (hwc->config_base) {
> case AMDGPU_PMU_EVENT_CONFIG_TYPE_DF:
> case AMDGPU_PMU_EVENT_CONFIG_TYPE_XGMI:
> @@ -289,7 +288,7 @@ static void amdgpu_perf_read(struct perf_event *event)
> count = 0;
> break;
> }
> - } while (local64_cmpxchg(&hwc->prev_count, prev, count) != prev);
> + } while (!local64_try_cmpxchg(&hwc->prev_count, &prev, count));
>
> local64_add(count - prev, &event->count);
> }
> --
> 2.41.0
>
