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Message-ID: <ZTb6azSfTV+LRGYu@pollux>
Date: Tue, 24 Oct 2023 00:57:47 +0200
From: Danilo Krummrich <dakr@...hat.com>
To: Boris Brezillon <boris.brezillon@...labora.com>
Cc: airlied@...il.com, daniel@...ll.ch, matthew.brost@...el.com,
christian.koenig@....com, faith.ekstrand@...labora.com,
luben.tuikov@....com, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-misc-next v2] drm/sched: implement dynamic job-flow
control
On Tue, Oct 10, 2023 at 09:41:51AM +0200, Boris Brezillon wrote:
> On Tue, 10 Oct 2023 00:35:53 +0200
> Danilo Krummrich <dakr@...hat.com> wrote:
>
> > Currently, job flow control is implemented simply by limiting the number
> > of jobs in flight. Therefore, a scheduler is initialized with a
> > submission limit that corresponds to the number of jobs which can be
> > sent to the hardware.
> >
> > This implies that for each job, drivers need to account for the maximum
> > job size possible in order to not overflow the ring buffer.
> >
> > However, there are drivers, such as Nouveau, where the job size has a
> > rather large range. For such drivers it can easily happen that job
> > submissions not even filling the ring by 1% can block subsequent
> > submissions, which, in the worst case, can lead to the ring run dry.
> >
> > In order to overcome this issue, allow for tracking the actual job size
> > instead of the number of jobs. Therefore, add a field to track a job's
> > submission credits, which represents the number of credits a job
> > contributes to the scheduler's submission limit.
> >
> > Signed-off-by: Danilo Krummrich <dakr@...hat.com>
> > ---
> > Changes in V2:
> > ==============
> > - fixed up influence on scheduling fairness due to consideration of a job's
> > size
> > - If we reach a ready entity in drm_sched_select_entity() but can't actually
> > queue a job from it due to size limitations, just give up and go to sleep
> > until woken up due to a pending job finishing, rather than continue to try
> > other entities.
> > - added a callback to dynamically update a job's credits (Boris)
> > - renamed 'units' to 'credits'
> > - fixed commit message and comments as requested by Luben
> > ---
> > drivers/gpu/drm/amd/amdgpu/amdgpu_job.c | 2 +-
> > drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c | 2 +-
> > drivers/gpu/drm/lima/lima_sched.c | 2 +-
> > drivers/gpu/drm/msm/msm_gem_submit.c | 2 +-
> > drivers/gpu/drm/nouveau/nouveau_sched.c | 2 +-
> > drivers/gpu/drm/panfrost/panfrost_drv.c | 2 +-
> > .../gpu/drm/scheduler/gpu_scheduler_trace.h | 2 +-
> > drivers/gpu/drm/scheduler/sched_entity.c | 5 +-
> > drivers/gpu/drm/scheduler/sched_main.c | 101 +++++++++++++-----
> > drivers/gpu/drm/v3d/v3d_gem.c | 2 +-
> > include/drm/gpu_scheduler.h | 33 ++++--
> > 11 files changed, 115 insertions(+), 40 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > index 78476bc75b4e..d54daaf64bf1 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > @@ -115,7 +115,7 @@ int amdgpu_job_alloc(struct amdgpu_device *adev, struct amdgpu_vm *vm,
> > if (!entity)
> > return 0;
> >
> > - return drm_sched_job_init(&(*job)->base, entity, owner);
> > + return drm_sched_job_init(&(*job)->base, entity, 1, owner);
> > }
> >
> > int amdgpu_job_alloc_with_ib(struct amdgpu_device *adev,
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
> > index 45403ea38906..74a446711207 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
> > @@ -538,7 +538,7 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void *data,
> >
> > ret = drm_sched_job_init(&submit->sched_job,
> > &ctx->sched_entity[args->pipe],
> > - submit->ctx);
> > + 1, submit->ctx);
> > if (ret)
> > goto err_submit_put;
> >
> > diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
> > index 50c2075228aa..5dc6678e1eb9 100644
> > --- a/drivers/gpu/drm/lima/lima_sched.c
> > +++ b/drivers/gpu/drm/lima/lima_sched.c
> > @@ -123,7 +123,7 @@ int lima_sched_task_init(struct lima_sched_task *task,
> > for (i = 0; i < num_bos; i++)
> > drm_gem_object_get(&bos[i]->base.base);
> >
> > - err = drm_sched_job_init(&task->base, &context->base, vm);
> > + err = drm_sched_job_init(&task->base, &context->base, 1, vm);
> > if (err) {
> > kfree(task->bos);
> > return err;
> > diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> > index 3f1aa4de3b87..6d230c38e4f5 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> > +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> > @@ -48,7 +48,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev,
> > return ERR_PTR(ret);
> > }
> >
> > - ret = drm_sched_job_init(&submit->base, queue->entity, queue);
> > + ret = drm_sched_job_init(&submit->base, queue->entity, 1, queue);
> > if (ret) {
> > kfree(submit->hw_fence);
> > kfree(submit);
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_sched.c b/drivers/gpu/drm/nouveau/nouveau_sched.c
> > index f26a814a9920..e991426d86e4 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_sched.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_sched.c
> > @@ -89,7 +89,7 @@ nouveau_job_init(struct nouveau_job *job,
> >
> > }
> >
> > - ret = drm_sched_job_init(&job->base, &entity->base, NULL);
> > + ret = drm_sched_job_init(&job->base, &entity->base, 1, NULL);
> > if (ret)
> > goto err_free_chains;
> >
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> > index b834777b409b..54d1c19bea84 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> > +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> > @@ -274,7 +274,7 @@ static int panfrost_ioctl_submit(struct drm_device *dev, void *data,
> >
> > ret = drm_sched_job_init(&job->base,
> > &file_priv->sched_entity[slot],
> > - NULL);
> > + 1, NULL);
> > if (ret)
> > goto out_put_job;
> >
> > diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> > index 3143ecaaff86..2e4ffdecc5dc 100644
> > --- a/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> > +++ b/drivers/gpu/drm/scheduler/gpu_scheduler_trace.h
> > @@ -51,7 +51,7 @@ DECLARE_EVENT_CLASS(drm_sched_job,
> > __assign_str(name, sched_job->sched->name);
> > __entry->job_count = spsc_queue_count(&entity->job_queue);
> > __entry->hw_job_count = atomic_read(
> > - &sched_job->sched->hw_rq_count);
> > + &sched_job->sched->submission_count);
> > ),
> > TP_printk("entity=%p, id=%llu, fence=%p, ring=%s, job count:%u, hw job count:%d",
> > __entry->entity, __entry->id,
> > diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> > index 437c50867c99..6395090d5784 100644
> > --- a/drivers/gpu/drm/scheduler/sched_entity.c
> > +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> > @@ -401,7 +401,8 @@ static void drm_sched_entity_wakeup(struct dma_fence *f,
> > container_of(cb, struct drm_sched_entity, cb);
> >
> > drm_sched_entity_clear_dep(f, cb);
> > - drm_sched_wakeup_if_can_queue(drm_sched_entity_to_scheduler(entity));
> > + drm_sched_wakeup_if_can_queue(drm_sched_entity_to_scheduler(entity),
> > + entity);
> > }
> >
> > /**
> > @@ -645,7 +646,7 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
> > if (fifo)
> > drm_sched_rq_update_fifo(entity, submit_ts);
> >
> > - drm_sched_wakeup_if_can_queue(sched);
> > + drm_sched_wakeup_if_can_queue(sched, entity);
> > }
> > }
> > EXPORT_SYMBOL(drm_sched_entity_push_job);
> > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > index 88ef8be2d3c7..da86dd0782d6 100644
> > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > @@ -93,6 +93,9 @@ int drm_sched_policy_default = DRM_SCHED_POLICY_FIFO;
> > MODULE_PARM_DESC(sched_policy, "Specify the scheduling policy for entities on a run-queue, " __stringify(DRM_SCHED_POLICY_RR) " = Round Robin, " __stringify(DRM_SCHED_POLICY_FIFO) " = FIFO (default).");
> > module_param_named(sched_policy, drm_sched_policy_default, int, 0444);
> >
> > +static bool drm_sched_can_queue(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_entity *entity);
>
> Nit: can we move the function instead of adding this forward
> declaration? I know it tends to screw up the diff, so maybe do it in 2
> steps.
Sure, gonna move it up.
>
> > +
> > static __always_inline bool drm_sched_entity_compare_before(struct rb_node *a,
> > const struct rb_node *b)
> > {
> > @@ -212,13 +215,15 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
> > /**
> > * drm_sched_rq_select_entity_rr - Select an entity which could provide a job to run
> > *
> > + * @sched: the gpu scheduler
> > * @rq: scheduler run queue to check.
> > * @dequeue: dequeue selected entity
> > *
> > * Try to find a ready entity, returns NULL if none found.
> > */
> > static struct drm_sched_entity *
> > -drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq, bool dequeue)
> > +drm_sched_rq_select_entity_rr(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_rq *rq, bool dequeue)
> > {
> > struct drm_sched_entity *entity;
> >
> > @@ -228,6 +233,12 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq, bool dequeue)
> > if (entity) {
> > list_for_each_entry_continue(entity, &rq->entities, list) {
> > if (drm_sched_entity_is_ready(entity)) {
> > + /* If we can't queue yet, preserve the current
> > + * entity in terms of fairness.
> > + */
> > + if (!drm_sched_can_queue(sched, entity))
> > + goto out;
> > +
> > if (dequeue) {
> > rq->current_entity = entity;
> > reinit_completion(&entity->entity_idle);
> > @@ -239,8 +250,13 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq, bool dequeue)
> > }
> >
> > list_for_each_entry(entity, &rq->entities, list) {
> > -
> > if (drm_sched_entity_is_ready(entity)) {
> > + /* If we can't queue yet, preserve the current entity in
> > + * terms of fairness.
> > + */
> > + if (!drm_sched_can_queue(sched, entity))
> > + goto out;
> > +
> > if (dequeue) {
> > rq->current_entity = entity;
> > reinit_completion(&entity->entity_idle);
> > @@ -253,21 +269,23 @@ drm_sched_rq_select_entity_rr(struct drm_sched_rq *rq, bool dequeue)
> > break;
> > }
> >
> > +out:
> > spin_unlock(&rq->lock);
> > -
> > return NULL;
> > }
> >
> > /**
> > * drm_sched_rq_select_entity_fifo - Select an entity which provides a job to run
> > *
> > + * @sched: the gpu scheduler
> > * @rq: scheduler run queue to check.
> > * @dequeue: dequeue selected entity
> > *
> > * Find oldest waiting ready entity, returns NULL if none found.
> > */
> > static struct drm_sched_entity *
> > -drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq, bool dequeue)
> > +drm_sched_rq_select_entity_fifo(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_rq *rq, bool dequeue)
> > {
> > struct rb_node *rb;
> >
> > @@ -277,6 +295,15 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq, bool dequeue)
> >
> > entity = rb_entry(rb, struct drm_sched_entity, rb_tree_node);
> > if (drm_sched_entity_is_ready(entity)) {
> > + /* If we can't queue yet, don't pick another entity
> > + * which's job might fit and wait until we got space for
> > + * this one in terms of fairness.
> > + */
> > + if (!drm_sched_can_queue(sched, entity)) {
> > + spin_unlock(&rq->lock);
> > + return NULL;
> > + }
> > +
> > if (dequeue) {
> > rq->current_entity = entity;
> > reinit_completion(&entity->entity_idle);
> > @@ -302,13 +329,32 @@ static void drm_sched_run_job_queue(struct drm_gpu_scheduler *sched)
> > /**
> > * drm_sched_can_queue -- Can we queue more to the hardware?
> > * @sched: scheduler instance
> > + * @entity: the scheduler entity
> > *
> > - * Return true if we can push more jobs to the hw, otherwise false.
> > + * Return true if we can push at least one more job from @entity, false
> > + * otherwise.
> > */
> > -static bool drm_sched_can_queue(struct drm_gpu_scheduler *sched)
> > +static bool drm_sched_can_queue(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_entity *entity)
> > {
> > - return atomic_read(&sched->hw_rq_count) <
> > - sched->hw_submission_limit;
> > + struct drm_sched_job *s_job;
> > +
> > + s_job = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
> > + if (!s_job)
> > + return false;
> > +
> > + if (sched->ops->update_job_credits) {
> > + u32 credits = sched->ops->update_job_credits(s_job);
> > +
> > + if (credits)
> > + s_job->submission_credits = credits;
> > + }
> > +
> > + WARN_ON(s_job->submission_credits > sched->submission_limit);
> > +
> > + return (sched->submission_limit -
> > + atomic_read(&sched->submission_count)) >=
>
> Nit: might be clearer with a dummy drm_sched_available_credits()
> helper:
Sure, why not.
>
> static u32
> drm_sched_available_credits(struct drm_gpu_scheduler *sched)
> {
> return sched->submission_limit -
> atomic_read(&sched->submission_count);
> }
>
> > + s_job->submission_credits;
> > }
> >
> > /**
> > @@ -325,12 +371,10 @@ drm_sched_select_entity(struct drm_gpu_scheduler *sched, bool dequeue)
> > struct drm_sched_entity *entity;
> > int i;
> >
> > - if (!drm_sched_can_queue(sched))
> > - return NULL;
> > -
> > if (sched->single_entity) {
> > if (!READ_ONCE(sched->single_entity->stopped) &&
> > - drm_sched_entity_is_ready(sched->single_entity))
> > + drm_sched_entity_is_ready(sched->single_entity) &&
> > + drm_sched_can_queue(sched, sched->single_entity))
> > return sched->single_entity;
> >
> > return NULL;
> > @@ -339,9 +383,11 @@ drm_sched_select_entity(struct drm_gpu_scheduler *sched, bool dequeue)
> > /* Kernel run queue has higher priority than normal run queue*/
> > for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
> > entity = sched->sched_policy == DRM_SCHED_POLICY_FIFO ?
> > - drm_sched_rq_select_entity_fifo(&sched->sched_rq[i],
> > + drm_sched_rq_select_entity_fifo(sched,
> > + &sched->sched_rq[i],
> > dequeue) :
> > - drm_sched_rq_select_entity_rr(&sched->sched_rq[i],
> > + drm_sched_rq_select_entity_rr(sched,
> > + &sched->sched_rq[i],
> > dequeue);
> > if (entity)
> > break;
> > @@ -399,7 +445,7 @@ static void drm_sched_job_done(struct drm_sched_job *s_job, int result)
> > struct drm_sched_fence *s_fence = s_job->s_fence;
> > struct drm_gpu_scheduler *sched = s_fence->sched;
> >
> > - atomic_dec(&sched->hw_rq_count);
> > + atomic_sub(s_job->submission_credits, &sched->submission_count);
> > atomic_dec(sched->score);
> >
> > trace_drm_sched_process_job(s_fence);
> > @@ -622,7 +668,8 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
> > &s_job->cb)) {
> > dma_fence_put(s_job->s_fence->parent);
> > s_job->s_fence->parent = NULL;
> > - atomic_dec(&sched->hw_rq_count);
> > + atomic_sub(s_job->submission_credits,
> > + &sched->submission_count);
> > } else {
> > /*
> > * remove job from pending_list.
> > @@ -683,7 +730,7 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
> > list_for_each_entry_safe(s_job, tmp, &sched->pending_list, list) {
> > struct dma_fence *fence = s_job->s_fence->parent;
> >
> > - atomic_inc(&sched->hw_rq_count);
> > + atomic_add(s_job->submission_credits, &sched->submission_count);
> >
> > if (!full_recovery)
> > continue;
> > @@ -764,6 +811,8 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs);
> > * drm_sched_job_init - init a scheduler job
> > * @job: scheduler job to init
> > * @entity: scheduler entity to use
> > + * @submission_credits: the number of credits this job contributes to the
> > + * schdulers submission limit
> > * @owner: job owner for debugging
> > *
> > * Refer to drm_sched_entity_push_job() documentation
> > @@ -781,6 +830,7 @@ EXPORT_SYMBOL(drm_sched_resubmit_jobs);
> > */
> > int drm_sched_job_init(struct drm_sched_job *job,
> > struct drm_sched_entity *entity,
> > + u32 submission_credits,
> > void *owner)
> > {
> > if (!entity->rq && !entity->single_sched)
> > @@ -792,6 +842,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
> > return -ENOMEM;
> >
> > INIT_LIST_HEAD(&job->list);
> > + job->submission_credits = submission_credits ? submission_credits : 1;
> >
> > xa_init_flags(&job->dependencies, XA_FLAGS_ALLOC);
> >
> > @@ -1004,12 +1055,14 @@ EXPORT_SYMBOL(drm_sched_job_cleanup);
> > /**
> > * drm_sched_wakeup_if_can_queue - Wake up the scheduler
> > * @sched: scheduler instance
> > + * @entity: the scheduler entity
> > *
> > * Wake up the scheduler if we can queue jobs.
> > */
> > -void drm_sched_wakeup_if_can_queue(struct drm_gpu_scheduler *sched)
> > +void drm_sched_wakeup_if_can_queue(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_entity *entity)
> > {
> > - if (drm_sched_can_queue(sched))
> > + if (drm_sched_can_queue(sched, entity))
> > drm_sched_run_job_queue(sched);
> > }
> >
> > @@ -1147,7 +1200,7 @@ static void drm_sched_run_job_work(struct work_struct *w)
> >
> > s_fence = sched_job->s_fence;
> >
> > - atomic_inc(&sched->hw_rq_count);
> > + atomic_add(sched_job->submission_credits, &sched->submission_count);
> > drm_sched_job_begin(sched_job);
> >
> > trace_drm_run_job(sched_job, entity);
> > @@ -1183,7 +1236,7 @@ static void drm_sched_run_job_work(struct work_struct *w)
> > * @ops: backend operations for this scheduler
> > * @submit_wq: workqueue to use for submission. If NULL, an ordered wq is
> > * allocated and used
> > - * @hw_submission: number of hw submissions that can be in flight
> > + * @max_submission_credits: number of submission credits that can be in flight
> > * @hang_limit: number of times to allow a job to hang before dropping it
> > * @timeout: timeout value in jiffies for the scheduler
> > * @timeout_wq: workqueue to use for timeout work. If NULL, the system_wq is
> > @@ -1198,7 +1251,7 @@ static void drm_sched_run_job_work(struct work_struct *w)
> > int drm_sched_init(struct drm_gpu_scheduler *sched,
> > const struct drm_sched_backend_ops *ops,
> > struct workqueue_struct *submit_wq,
> > - unsigned hw_submission, unsigned hang_limit,
> > + unsigned max_submission_credits, unsigned hang_limit,
> > long timeout, struct workqueue_struct *timeout_wq,
> > atomic_t *score, const char *name,
> > enum drm_sched_policy sched_policy,
> > @@ -1211,7 +1264,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
> >
> > sched->ops = ops;
> > sched->single_entity = NULL;
> > - sched->hw_submission_limit = hw_submission;
> > + sched->submission_limit = max_submission_credits;
> > sched->name = name;
> > if (!submit_wq) {
> > sched->submit_wq = alloc_ordered_workqueue(name, 0);
> > @@ -1238,7 +1291,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
> > init_waitqueue_head(&sched->job_scheduled);
> > INIT_LIST_HEAD(&sched->pending_list);
> > spin_lock_init(&sched->job_list_lock);
> > - atomic_set(&sched->hw_rq_count, 0);
> > + atomic_set(&sched->submission_count, 0);
> > INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
> > INIT_WORK(&sched->work_run_job, drm_sched_run_job_work);
> > INIT_WORK(&sched->work_free_job, drm_sched_free_job_work);
> > diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> > index 2e94ce788c71..8479e5302f7b 100644
> > --- a/drivers/gpu/drm/v3d/v3d_gem.c
> > +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> > @@ -417,7 +417,7 @@ v3d_job_init(struct v3d_dev *v3d, struct drm_file *file_priv,
> > job->free = free;
> >
> > ret = drm_sched_job_init(&job->base, &v3d_priv->sched_entity[queue],
> > - v3d_priv);
> > + 1, v3d_priv);
> > if (ret)
> > goto fail;
> >
> > diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> > index 27f5778bbd6d..c4a53b259585 100644
> > --- a/include/drm/gpu_scheduler.h
> > +++ b/include/drm/gpu_scheduler.h
> > @@ -329,6 +329,8 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
> > * @sched: the scheduler instance on which this job is scheduled.
> > * @s_fence: contains the fences for the scheduling of job.
> > * @finish_cb: the callback for the finished fence.
> > + * @submission_credits: the number of submission credits this job contributes to
> > + * the scheduler
> > * @work: Helper to reschdeule job kill to different context.
> > * @id: a unique id assigned to each job scheduled on the scheduler.
> > * @karma: increment on every hang caused by this job. If this exceeds the hang
> > @@ -348,6 +350,8 @@ struct drm_sched_job {
> > struct drm_gpu_scheduler *sched;
> > struct drm_sched_fence *s_fence;
> >
> > + u32 submission_credits;
> > +
> > /*
> > * work is used only after finish_cb has been used and will not be
> > * accessed anymore.
> > @@ -471,6 +475,21 @@ struct drm_sched_backend_ops {
> > * and it's time to clean it up.
> > */
> > void (*free_job)(struct drm_sched_job *sched_job);
> > +
> > + /**
> > + * @update_job_credits: Called once the scheduler is considering this
> > + * job for execution.
> > + *
> > + * Drivers may use this to update the job's submission credits, which is
> > + * useful to e.g. deduct the number of native fences which have been
> > + * signaled meanwhile.
> > + *
> > + * The callback must either return the new number of submission credits
> > + * for the given job, or zero if no update is required.
>
> Any reason for having this special zero-means-no-update case? I mean,
> drivers could just return sched_job->submission_credits if nothing
> changed, and that would simplify the semantics IMHO. Another option, if
I think I just did this because I thought it's a clever way to get rid of the
need to deal with zero-sized jobs, which do not make much sense. In
drm_sched_job_init() passing a zero job size defaults to one, which I think is
reasonable. Doing the same thing here is more likely to hide a bug. However, the
same is probably true for 'zero means no update' though. Maybe we should just
WARN() in such a case.
> we want to avoid the sched_job->submission_credits assignment when
> nothing changes would be to make it a void function and let it update
> the sched_job->submission_credits directly.
Sure, that's an option as well. However, I'd probably prefer the new job size to
be the return value. Having to sanity check job->submission_credits afterwards
isn't that nice either.
>
> > + *
> > + * This callback is optional.
> > + */
> > + u32 (*update_job_credits)(struct drm_sched_job *sched_job);
> > };
> >
> > /**
> > @@ -478,14 +497,14 @@ struct drm_sched_backend_ops {
> > *
> > * @ops: backend operations provided by the driver.
> > * @single_entity: Single entity for the scheduler
> > - * @hw_submission_limit: the max size of the hardware queue.
> > + * @submission_limit: the maximim number of submission credits
> > + * @submission_count: the number of submission credits in flight
>
> Now that we use the term credit at the job level, I'd recommend using
> it here as well, for consistency. Maybe
> s/submission_count/assigned_credits/ and
> s/submission_limit/max_credits/?
IIRC, Luben is proposing something similar. Gonna change that.
>
> > * @timeout: the time after which a job is removed from the scheduler.
> > * @name: name of the ring for which this scheduler is being used.
> > * @sched_rq: priority wise array of run queues.
> > * @job_scheduled: once @drm_sched_entity_do_release is called the scheduler
> > * waits on this wait queue until all the scheduled jobs are
> > * finished.
> > - * @hw_rq_count: the number of jobs currently in the hardware queue.
> > * @job_id_count: used to assign unique id to the each job.
> > * @submit_wq: workqueue used to queue @work_run_job and @work_free_job
> > * @timeout_wq: workqueue used to queue @work_tdr
> > @@ -511,12 +530,12 @@ struct drm_sched_backend_ops {
> > struct drm_gpu_scheduler {
> > const struct drm_sched_backend_ops *ops;
> > struct drm_sched_entity *single_entity;
> > - uint32_t hw_submission_limit;
> > + u32 submission_limit;
> > + atomic_t submission_count;
> > long timeout;
> > const char *name;
> > struct drm_sched_rq sched_rq[DRM_SCHED_PRIORITY_COUNT];
> > wait_queue_head_t job_scheduled;
> > - atomic_t hw_rq_count;
> > atomic64_t job_id_count;
> > struct workqueue_struct *submit_wq;
> > struct workqueue_struct *timeout_wq;
> > @@ -539,7 +558,7 @@ struct drm_gpu_scheduler {
> > int drm_sched_init(struct drm_gpu_scheduler *sched,
> > const struct drm_sched_backend_ops *ops,
> > struct workqueue_struct *submit_wq,
> > - uint32_t hw_submission, unsigned hang_limit,
> > + uint32_t max_submission_credits, unsigned hang_limit,
> > long timeout, struct workqueue_struct *timeout_wq,
> > atomic_t *score, const char *name,
> > enum drm_sched_policy sched_policy,
> > @@ -548,6 +567,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
> > void drm_sched_fini(struct drm_gpu_scheduler *sched);
> > int drm_sched_job_init(struct drm_sched_job *job,
> > struct drm_sched_entity *entity,
> > + u32 submission_credits,
> > void *owner);
>
> Nit: we keep adding parameters to functions like drm_sched_init() and
> drm_sched_job_init() and every time this implies patching all call
> sites to pass the new default value. In a sense, that's a good thing,
> because it forces driver maintainers to check that the patch does the
> right thing. But overall, it makes the driver code harder to read, in
> that it forces the reader to go check the function prototype to figure
> out what these magic 1 or NULL values mean. So, I wonder if we
> shouldn't move to a model where we pass struct drm_sched[_job]_params
> objects around:
>
> const struct drm_sched_job_params params = {
> .entity = xxx,
> .submission_credits = xxx,
> .owner = THIS_MODULE,
> };
>
> ...
>
> ret = drm_sched_job_init(job, ¶ms);
>
> It would also let us add new fields and pick the right default when
> this field is zero, thus preventing cross-driver updates when such a
> field is added.
Yes, the same is true for drm_sched_init() - that's something for a separate
patch though.
>
> > void drm_sched_job_arm(struct drm_sched_job *job);
> > int drm_sched_job_add_dependency(struct drm_sched_job *job,
> > @@ -570,7 +590,8 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
> >
> > void drm_sched_tdr_queue_imm(struct drm_gpu_scheduler *sched);
> > void drm_sched_job_cleanup(struct drm_sched_job *job);
> > -void drm_sched_wakeup_if_can_queue(struct drm_gpu_scheduler *sched);
> > +void drm_sched_wakeup_if_can_queue(struct drm_gpu_scheduler *sched,
> > + struct drm_sched_entity *entity);
> > bool drm_sched_submit_ready(struct drm_gpu_scheduler *sched);
> > void drm_sched_submit_stop(struct drm_gpu_scheduler *sched);
> > void drm_sched_submit_start(struct drm_gpu_scheduler *sched);
>
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