[PATCH] drm/nouveau: wait for the exclusive fence after the shared ones v2
Stefan Fritsch
sf at sfritsch.de
Sat Dec 11 09:59:23 UTC 2021
On 09.12.21 11:23, Christian König wrote:
> Always waiting for the exclusive fence resulted on some performance
> regressions. So try to wait for the shared fences first, then the
> exclusive fence should always be signaled already.
>
> v2: fix incorrectly placed "(", add some comment why we do this.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
Tested-by: Stefan Fritsch <sf at sfritsch.de>
Please also add a cc for linux-stable, so that this is fixed in 5.15.x
Cheers,
Stefan
> ---
> drivers/gpu/drm/nouveau/nouveau_fence.c | 28 +++++++++++++------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index 05d0b3eb3690..0ae416aa76dc 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -353,15 +353,22 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, bool e
>
> if (ret)
> return ret;
> - }
>
> - fobj = dma_resv_shared_list(resv);
> - fence = dma_resv_excl_fence(resv);
> + fobj = NULL;
> + } else {
> + fobj = dma_resv_shared_list(resv);
> + }
>
> - if (fence) {
> + /* Waiting for the exclusive fence first causes performance regressions
> + * under some circumstances. So manually wait for the shared ones first.
> + */
> + for (i = 0; i < (fobj ? fobj->shared_count : 0) && !ret; ++i) {
> struct nouveau_channel *prev = NULL;
> bool must_wait = true;
>
> + fence = rcu_dereference_protected(fobj->shared[i],
> + dma_resv_held(resv));
> +
> f = nouveau_local_fence(fence, chan->drm);
> if (f) {
> rcu_read_lock();
> @@ -373,20 +380,13 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, bool e
>
> if (must_wait)
> ret = dma_fence_wait(fence, intr);
> -
> - return ret;
> }
>
> - if (!exclusive || !fobj)
> - return ret;
> -
> - for (i = 0; i < fobj->shared_count && !ret; ++i) {
> + fence = dma_resv_excl_fence(resv);
> + if (fence) {
> struct nouveau_channel *prev = NULL;
> bool must_wait = true;
>
> - fence = rcu_dereference_protected(fobj->shared[i],
> - dma_resv_held(resv));
> -
> f = nouveau_local_fence(fence, chan->drm);
> if (f) {
> rcu_read_lock();
> @@ -398,6 +398,8 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, bool e
>
> if (must_wait)
> ret = dma_fence_wait(fence, intr);
> +
> + return ret;
> }
>
> return ret;
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