From a6149f0393699308fb00149be913044977bceb56 Mon Sep 17 00:00:00 2001 From: Matthew Brost Date: Mon, 30 Oct 2023 20:24:36 -0700 Subject: drm/sched: Convert drm scheduler to use a work queue rather than kthread In Xe, the new Intel GPU driver, a choice has made to have a 1 to 1 mapping between a drm_gpu_scheduler and drm_sched_entity. At first this seems a bit odd but let us explain the reasoning below. 1. In Xe the submission order from multiple drm_sched_entity is not guaranteed to be the same completion even if targeting the same hardware engine. This is because in Xe we have a firmware scheduler, the GuC, which allowed to reorder, timeslice, and preempt submissions. If a using shared drm_gpu_scheduler across multiple drm_sched_entity, the TDR falls apart as the TDR expects submission order == completion order. Using a dedicated drm_gpu_scheduler per drm_sched_entity solve this problem. 2. In Xe submissions are done via programming a ring buffer (circular buffer), a drm_gpu_scheduler provides a limit on number of jobs, if the limit of number jobs is set to RING_SIZE / MAX_SIZE_PER_JOB we get flow control on the ring for free. A problem with this design is currently a drm_gpu_scheduler uses a kthread for submission / job cleanup. This doesn't scale if a large number of drm_gpu_scheduler are used. To work around the scaling issue, use a worker rather than kthread for submission / job cleanup. v2: - (Rob Clark) Fix msm build - Pass in run work queue v3: - (Boris) don't have loop in worker v4: - (Tvrtko) break out submit ready, stop, start helpers into own patch v5: - (Boris) default to ordered work queue v6: - (Luben / checkpatch) fix alignment in msm_ringbuffer.c - (Luben) s/drm_sched_submit_queue/drm_sched_wqueue_enqueue - (Luben) Update comment for drm_sched_wqueue_enqueue - (Luben) Positive check for submit_wq in drm_sched_init - (Luben) s/alloc_submit_wq/own_submit_wq v7: - (Luben) s/drm_sched_wqueue_enqueue/drm_sched_run_job_queue v8: - (Luben) Adjust var names / comments Signed-off-by: Matthew Brost Reviewed-by: Luben Tuikov Link: https://lore.kernel.org/r/20231031032439.1558703-3-matthew.brost@intel.com Signed-off-by: Luben Tuikov --- drivers/gpu/drm/msm/msm_ringbuffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/gpu/drm/msm/msm_ringbuffer.c') diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c index 95257ab0185d..4968568e3b54 100644 --- a/drivers/gpu/drm/msm/msm_ringbuffer.c +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c @@ -94,7 +94,7 @@ struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id, /* currently managing hangcheck ourselves: */ sched_timeout = MAX_SCHEDULE_TIMEOUT; - ret = drm_sched_init(&ring->sched, &msm_sched_ops, + ret = drm_sched_init(&ring->sched, &msm_sched_ops, NULL, DRM_SCHED_PRIORITY_COUNT, num_hw_submissions, 0, sched_timeout, NULL, NULL, to_msm_bo(ring->bo)->name, gpu->dev->dev); -- cgit v1.2.3