On Fri, Apr 26, 2019 at 4:08 AM Michel Dänzer <mic...@daenzer.net> wrote:
> On 2019-04-26 4:06 a.m., Marek Olšák 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. > > Nice idea. Not sure offhand about all ramifications, but certainly worth > a go. > > > > 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; > > This might be slightly misleading, as there can still be two frames in > flight (on the GPU) at the same time. Might be better to leave this at 2 > (so Nine isn't affected) and adjust its treatment in > src/gallium/state_trackers/dri/dri_drawable.c . > When dri_flush is waiting, there can be at most 2 frames submitted and not finished (that's why it's waiting). When dri_flush is done, there is at most 1 frame submitted and not finished. The CAP is enforced by dri_flush. Marek
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