On Fri, Oct 06, 2023 at 08:59:15AM +0100, Tvrtko Ursulin wrote:
>
> On 05/10/2023 05:13, Luben Tuikov wrote:
> > On 2023-10-04 23:33, Matthew Brost wrote:
> > > On Tue, Sep 26, 2023 at 11:32:10PM -0400, Luben Tuikov wrote:
> > > > Hi,
> > > >
> > > > On 2023-09-19 01:01, Matthew Brost wrote:
> > > > > 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
> > > > >
> > > > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > > > > ---
> > > > > drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
> > > > > drivers/gpu/drm/etnaviv/etnaviv_sched.c | 2 +-
> > > > > drivers/gpu/drm/lima/lima_sched.c | 2 +-
> > > > > drivers/gpu/drm/msm/msm_ringbuffer.c | 2 +-
> > > > > drivers/gpu/drm/nouveau/nouveau_sched.c | 2 +-
> > > > > drivers/gpu/drm/panfrost/panfrost_job.c | 2 +-
> > > > > drivers/gpu/drm/scheduler/sched_main.c | 118 ++++++++++-----------
> > > > > drivers/gpu/drm/v3d/v3d_sched.c | 10 +-
> > > > > include/drm/gpu_scheduler.h | 14 ++-
> > > > > 9 files changed, 79 insertions(+), 75 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > index e366f61c3aed..16f3cfe1574a 100644
> > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > @@ -2279,7 +2279,7 @@ static int amdgpu_device_init_schedulers(struct amdgpu_device *adev)
> > > > > break;
> > > > > }
> > > > > - r = drm_sched_init(&ring->sched, &amdgpu_sched_ops,
> > > > > + r = drm_sched_init(&ring->sched, &amdgpu_sched_ops, NULL,
> > > > > ring->num_hw_submission, 0,
> > > > > timeout, adev->reset_domain->wq,
> > > > > ring->sched_score, ring->name,
> > > > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> > > > > index 345fec6cb1a4..618a804ddc34 100644
> > > > > --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> > > > > +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
> > > > > @@ -134,7 +134,7 @@ int etnaviv_sched_init(struct etnaviv_gpu *gpu)
> > > > > {
> > > > > int ret;
> > > > > - ret = drm_sched_init(&gpu->sched, &etnaviv_sched_ops,
> > > > > + ret = drm_sched_init(&gpu->sched, &etnaviv_sched_ops, NULL,
> > > > > etnaviv_hw_jobs_limit, etnaviv_job_hang_limit,
> > > > > msecs_to_jiffies(500), NULL, NULL,
> > > > > dev_name(gpu->dev), gpu->dev);
> > > > > diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
> > > > > index ffd91a5ee299..8d858aed0e56 100644
> > > > > --- a/drivers/gpu/drm/lima/lima_sched.c
> > > > > +++ b/drivers/gpu/drm/lima/lima_sched.c
> > > > > @@ -488,7 +488,7 @@ int lima_sched_pipe_init(struct lima_sched_pipe *pipe, const char *name)
> > > > > INIT_WORK(&pipe->recover_work, lima_sched_recover_work);
> > > > > - return drm_sched_init(&pipe->base, &lima_sched_ops, 1,
> > > > > + return drm_sched_init(&pipe->base, &lima_sched_ops, NULL, 1,
> > > > > lima_job_hang_limit,
> > > > > msecs_to_jiffies(timeout), NULL,
> > > > > NULL, name, pipe->ldev->dev);
> > > > > diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
> > > > > index 40c0bc35a44c..b8865e61b40f 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,
> > > > > num_hw_submissions, 0, sched_timeout,
> > > > > NULL, NULL, to_msm_bo(ring->bo)->name, gpu->dev->dev);
> > > >
> > > > checkpatch.pl complains here about unmatched open parens.
> > > >
> > >
> > > Will fix and run checkpatch before posting next rev.
> > >
> > > > > if (ret) {
> > > > > diff --git a/drivers/gpu/drm/nouveau/nouveau_sched.c b/drivers/gpu/drm/nouveau/nouveau_sched.c
> > > > > index 88217185e0f3..d458c2227d4f 100644
> > > > > --- a/drivers/gpu/drm/nouveau/nouveau_sched.c
> > > > > +++ b/drivers/gpu/drm/nouveau/nouveau_sched.c
> > > > > @@ -429,7 +429,7 @@ int nouveau_sched_init(struct nouveau_drm *drm)
> > > > > if (!drm->sched_wq)
> > > > > return -ENOMEM;
> > > > > - return drm_sched_init(sched, &nouveau_sched_ops,
> > > > > + return drm_sched_init(sched, &nouveau_sched_ops, NULL,
> > > > > NOUVEAU_SCHED_HW_SUBMISSIONS, 0, job_hang_limit,
> > > > > NULL, NULL, "nouveau_sched", drm->dev->dev);
> > > > > }
> > > > > diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
> > > > > index 033f5e684707..326ca1ddf1d7 100644
> > > > > --- a/drivers/gpu/drm/panfrost/panfrost_job.c
> > > > > +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
> > > > > @@ -831,7 +831,7 @@ int panfrost_job_init(struct panfrost_device *pfdev)
> > > > > js->queue[j].fence_context = dma_fence_context_alloc(1);
> > > > > ret = drm_sched_init(&js->queue[j].sched,
> > > > > - &panfrost_sched_ops,
> > > > > + &panfrost_sched_ops, NULL,
> > > > > nentries, 0,
> > > > > msecs_to_jiffies(JOB_TIMEOUT_MS),
> > > > > pfdev->reset.wq,
> > > > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > > > > index e4fa62abca41..ee6281942e36 100644
> > > > > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > > > > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > > > > @@ -48,7 +48,6 @@
> > > > > * through the jobs entity pointer.
> > > > > */
> > > > > -#include <linux/kthread.h>
> > > > > #include <linux/wait.h>
> > > > > #include <linux/sched.h>
> > > > > #include <linux/completion.h>
> > > > > @@ -256,6 +255,16 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
> > > > > return rb ? rb_entry(rb, struct drm_sched_entity, rb_tree_node) : NULL;
> > > > > }
> > > > > +/**
> > > > > + * drm_sched_submit_queue - scheduler queue submission
> > > >
> > > > There is no verb in the description, and is not clear what
> > > > this function does unless one reads the code. Given that this
> > > > is DOC, this should be clearer here. Something like "queue
> > > > scheduler work to be executed" or something to that effect.
> > > >
> > >
> > > Will fix.
> > > > Coming back to this from reading the patch below, it was somewhat
> > > > unclear what "drm_sched_submit_queue()" does, since when reading
> > > > below, "submit" was being read by my mind as an adjective, as opposed
> > > > to a verb. Perhaps something like:
> > > >
> > > > drm_sched_queue_submit(), or
> > > > drm_sched_queue_exec(), or
> > > > drm_sched_queue_push(), or something to that effect. You pick. :-)
> > > >
> > >
> > > I prefer the name as is. In this patch we have:
> > >
> > > drm_sched_submit_queue()
> > > drm_sched_submit_start)
> > > drm_sched_submit_stop()
> > > drm_sched_submit_ready()
> > >
> > > I like all these functions start with 'drm_sched_submit' which allows
> > > for easy searching for the functions that touch the DRM scheduler
> > > submission state.
> > >
> > > With a little better doc are you fine with the names as is.
> >
> > Notice the following scheme in the naming,
> >
> > drm_sched_submit_queue()
> > drm_sched_submit_start)
> > drm_sched_submit_stop()
> > drm_sched_submit_ready()
> > \---+---/ \--+-/ \-+-/
> > | | +---> a verb
> > | +---------> should be a noun (something in the component)
> > +------------------> the kernel/software component
> >
> > And although "queue" can technically be used as a verb too, I'd rather it be "enqueue",
> > like this:
> >
> > drm_sched_submit_enqueue()
> >
> > And using "submit" as the noun of the component is a bit cringy,
> > since "submit" is really a verb, and it's cringy to make it a "state"
> > or an "object" we operate on in the DRM Scheduler. "Submission" is
> > a noun, but "submission enqueue/start/stop/ready" doesn't sound
> > very well thought out. "Submission" really is what the work-queue
> > does.
> >
> > I'd rather it be a real object, like for instance,
> >
> > drm_sched_wqueue_enqueue()
> > drm_sched_wqueue_start)
> > drm_sched_wqueue_stop()
> > drm_sched_wqueue_ready()
> >
How about:
drm_sched_submission_enqueue()
drm_sched_submission_start)
drm_sched_submission_stop()
drm_sched_submission_ready()
Matt
> > Which tells me that the component is the DRM Scheduler, the object is a/the work-queue,
> > and the last word as the verb, is the action we're performing on the object, i.e. the work-queue.
> > Plus, all these functions actually do operate on work-queues, directly or indirectly,
> > are new, so it's a win-win naming scheme.
> >
> > I think that that would be most likeable.
>
> FWIW I was suggesting not to encode the fact submit queue is implemented
> with a workqueue in the API name. IMO it would be nicer and less maintenance
> churn should something channge if the external components can be isolated
> from that detail.
>
> drm_sched_submit_queue_$verb? If not viewed as too verbose...
>
> Regards,
>
> Tvrtko
