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Date: Mon, 16 Aug 2021 17:38:19 +0200
From: Daniel Vetter <daniel@...ll.ch>
To: Christian König
<ckoenig.leichtzumerken@...il.com>
Cc: Rob Clark <robdclark@...il.com>, dri-devel@...ts.freedesktop.org,
linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
Daniel Vetter <daniel@...ll.ch>,
Rob Clark <robdclark@...omium.org>,
David Airlie <airlied@...ux.ie>,
Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
Tian Tao <tiantao6@...ilicon.com>,
Alex Deucher <alexander.deucher@....com>,
Luben Tuikov <luben.tuikov@....com>,
Andrey Grodzovsky <andrey.grodzovsky@....com>,
Steven Price <steven.price@....com>, Roy Sun <Roy.Sun@....com>,
Lee Jones <lee.jones@...aro.org>,
Jack Zhang <Jack.Zhang1@....com>,
open list <linux-kernel@...r.kernel.org>,
"open list:DMA BUFFER SHARING FRAMEWORK"
<linux-media@...r.kernel.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH v2 4/5] drm/scheduler: Add fence deadline support
On Mon, Aug 16, 2021 at 12:14:35PM +0200, Christian König wrote:
> Am 07.08.21 um 20:37 schrieb Rob Clark:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > As the finished fence is the one that is exposed to userspace, and
> > therefore the one that other operations, like atomic update, would
> > block on, we need to propagate the deadline from from the finished
> > fence to the actual hw fence.
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
I guess you're already letting the compositor run at a higher gpu priority
so that your deadline'd drm_sched_job isn't stuck behind the app rendering
the next frame?
I'm not sure whether you wire that one up as part of the conversion to
drm/sched. Without that I think we might need to ponder how we can do a
prio-boost for these, e.g. within a scheduling class we pick the jobs with
the nearest deadline first, before we pick others.
-Daniel
> > ---
> > drivers/gpu/drm/scheduler/sched_fence.c | 25 +++++++++++++++++++++++++
> > drivers/gpu/drm/scheduler/sched_main.c | 3 +++
> > include/drm/gpu_scheduler.h | 6 ++++++
> > 3 files changed, 34 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
> > index 69de2c76731f..f389dca44185 100644
> > --- a/drivers/gpu/drm/scheduler/sched_fence.c
> > +++ b/drivers/gpu/drm/scheduler/sched_fence.c
> > @@ -128,6 +128,30 @@ static void drm_sched_fence_release_finished(struct dma_fence *f)
> > dma_fence_put(&fence->scheduled);
> > }
> > +static void drm_sched_fence_set_deadline_finished(struct dma_fence *f,
> > + ktime_t deadline)
> > +{
> > + struct drm_sched_fence *fence = to_drm_sched_fence(f);
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&fence->lock, flags);
> > +
> > + /* If we already have an earlier deadline, keep it: */
> > + if (test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &f->flags) &&
> > + ktime_before(fence->deadline, deadline)) {
> > + spin_unlock_irqrestore(&fence->lock, flags);
> > + return;
> > + }
> > +
> > + fence->deadline = deadline;
> > + set_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT, &f->flags);
> > +
> > + spin_unlock_irqrestore(&fence->lock, flags);
> > +
> > + if (fence->parent)
> > + dma_fence_set_deadline(fence->parent, deadline);
> > +}
> > +
> > static const struct dma_fence_ops drm_sched_fence_ops_scheduled = {
> > .get_driver_name = drm_sched_fence_get_driver_name,
> > .get_timeline_name = drm_sched_fence_get_timeline_name,
> > @@ -138,6 +162,7 @@ static const struct dma_fence_ops drm_sched_fence_ops_finished = {
> > .get_driver_name = drm_sched_fence_get_driver_name,
> > .get_timeline_name = drm_sched_fence_get_timeline_name,
> > .release = drm_sched_fence_release_finished,
> > + .set_deadline = drm_sched_fence_set_deadline_finished,
> > };
> > struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f)
> > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > index a2a953693b45..3ab0900d3596 100644
> > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > @@ -818,6 +818,9 @@ static int drm_sched_main(void *param)
> > if (!IS_ERR_OR_NULL(fence)) {
> > s_fence->parent = dma_fence_get(fence);
> > + if (test_bit(DMA_FENCE_FLAG_HAS_DEADLINE_BIT,
> > + &s_fence->finished.flags))
> > + dma_fence_set_deadline(fence, s_fence->deadline);
>
> Maybe move this into a dma_sched_fence_set_parent() function.
>
> Apart from that looks good to me.
>
> Regards,
> Christian.
>
> > r = dma_fence_add_callback(fence, &sched_job->cb,
> > drm_sched_job_done_cb);
> > if (r == -ENOENT)
> > diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> > index d18af49fd009..0f08ade614ae 100644
> > --- a/include/drm/gpu_scheduler.h
> > +++ b/include/drm/gpu_scheduler.h
> > @@ -144,6 +144,12 @@ struct drm_sched_fence {
> > */
> > struct dma_fence finished;
> > + /**
> > + * @deadline: deadline set on &drm_sched_fence.finished which
> > + * potentially needs to be propagated to &drm_sched_fence.parent
> > + */
> > + ktime_t deadline;
> > +
> > /**
> > * @parent: the fence returned by &drm_sched_backend_ops.run_job
> > * when scheduling the job on hardware. We signal the
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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