On Thu, Apr 25, 2019 at 7:06 PM Marek Olšák <mar...@gmail.com> wrote:
>
> From: Marek Olšák <marek.ol...@amd.com>
>
> It's done by:
> - decrease the number of frames in flight by 1
> - flush before throttling in SwapBuffers
> (instead of wait-then-flush, do flush-then-wait)
>
> The improvement is apparent with Unigine Heaven.
>
> Previously:
> draw frame 2
> wait frame 0
> flush frame 2
> present frame 2
>
> The input lag is 2 frames.
>
> Now:
> draw frame 2
> flush frame 2
> wait frame 1
> present frame 2
>
> The input lag is 1 frame. Flushing is done before waiting, because
> otherwise the device would be idle after waiting.
>
> Nine is affected because it also uses the pipe cap.
> ---
> src/gallium/auxiliary/util/u_screen.c | 2 +-
> src/gallium/state_trackers/dri/dri_drawable.c | 20 +++++++++----------
> 2 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/src/gallium/auxiliary/util/u_screen.c
> b/src/gallium/auxiliary/util/u_screen.c
> index 27f51e0898e..410f17421e6 100644
> --- a/src/gallium/auxiliary/util/u_screen.c
> +++ b/src/gallium/auxiliary/util/u_screen.c
> @@ -349,21 +349,21 @@ u_pipe_screen_get_param_defaults(struct pipe_screen
> *pscreen,
> case PIPE_CAP_MAX_VARYINGS:
> return 8;
>
> case PIPE_CAP_COMPUTE_GRID_INFO_LAST_BLOCK:
> return 0;
>
> case PIPE_CAP_COMPUTE_SHADER_DERIVATIVES:
> return 0;
>
> case PIPE_CAP_MAX_FRAMES_IN_FLIGHT:
> - return 2;
> + return 1;
would it be safer to leave the current default and let drivers opt-in
to the lower # individually? I guess triple buffering would still be
better for some of the smaller gpu's?
disclaimer: I haven't tested this myself or looked very closely at the
dri code.. so could be misunderstanding something..
BR,
-R
>
> case PIPE_CAP_DMABUF:
> #ifdef PIPE_OS_LINUX
> return 1;
> #else
> return 0;
> #endif
>
> default:
> unreachable("bad PIPE_CAP_*");
> diff --git a/src/gallium/state_trackers/dri/dri_drawable.c
> b/src/gallium/state_trackers/dri/dri_drawable.c
> index 26bfdbecc53..c1de3bed9dd 100644
> --- a/src/gallium/state_trackers/dri/dri_drawable.c
> +++ b/src/gallium/state_trackers/dri/dri_drawable.c
> @@ -555,33 +555,33 @@ dri_flush(__DRIcontext *cPriv,
> *
> * This pulls a fence off the throttling queue and waits for it if the
> * number of fences on the throttling queue has reached the desired
> * number.
> *
> * Then flushes to insert a fence at the current rendering position,
> and
> * pushes that fence on the queue. This requires that the
> st_context_iface
> * flush method returns a fence even if there are no commands to flush.
> */
> struct pipe_screen *screen = drawable->screen->base.screen;
> - struct pipe_fence_handle *fence;
> + struct pipe_fence_handle *oldest_fence, *new_fence = NULL;
>
> - fence = swap_fences_pop_front(drawable);
> - if (fence) {
> - (void) screen->fence_finish(screen, NULL, fence,
> PIPE_TIMEOUT_INFINITE);
> - screen->fence_reference(screen, &fence, NULL);
> - }
> + st->flush(st, flush_flags, &new_fence);
>
> - st->flush(st, flush_flags, &fence);
> + oldest_fence = swap_fences_pop_front(drawable);
> + if (oldest_fence) {
> + screen->fence_finish(screen, NULL, oldest_fence,
> PIPE_TIMEOUT_INFINITE);
> + screen->fence_reference(screen, &oldest_fence, NULL);
> + }
>
> - if (fence) {
> - swap_fences_push_back(drawable, fence);
> - screen->fence_reference(screen, &fence, NULL);
> + if (new_fence) {
> + swap_fences_push_back(drawable, new_fence);
> + screen->fence_reference(screen, &new_fence, NULL);
> }
> }
> else if (flags & (__DRI2_FLUSH_DRAWABLE | __DRI2_FLUSH_CONTEXT)) {
> st->flush(st, flush_flags, NULL);
> }
>
> if (drawable) {
> drawable->flushing = FALSE;
> }
>
> --
> 2.17.1
>
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