Re: [Linaro-mm-sig] [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@chromium.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@chromium.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