[PATCH drm-misc-next v2] drm/sched: implement dynamic job-flow control
Danilo Krummrich
dakr at redhat.com
Thu Oct 12 02:10:20 UTC 2023
On 10/12/23 03:52, Luben Tuikov wrote:
> Hi,
>
> Thanks for fixing the title and submitting a v2 of this patch. Comments inlined below.
>
> On 2023-10-09 18:35, Danilo Krummrich 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 at redhat.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);
>> +
>> 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;
>> + }
>> +
>
> I wonder if here it would've been cleaner to just do,
>
> if (!drm_sched_can_queue(sched, entity)) {
> rb = NULL;
> break;
> }
>
> in order to follow the natural flow of the R-B tree search?
> In other words, the loop invariant becomes false, we exit the loop,
> unlock and return NULL.
>
> Yeah, let's do that.
>
>> 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)) >=
>> + 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;
>
> This mixing of the Xe patches and this patch is very, very annoying.
> Here and in RR picking the entity mix-up with "dequeue" which is
> now "peek"...
>
> I'd like to have applied this patch to drm-misc-next and inspect it further,
> but cannot chase around which version of the Xe patches this patch applies
> to, cleanly, so I'd really rather have had this patch on a clean drm-misc-next
> tree.
I pushed you a branch [1], it's based on drm-misc-next plus V4 of the sched changes for XE series.
I'll reply to the other comments tomorrow.
- Danilo
[1] https://gitlab.freedesktop.org/nouvelles/kernel/-/commits/sched-credits/
>
>>
>> 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
>
> Spelling: "schedulers"!
>
> Please run your patch through scripts/checkpatch.pl --strict and inspect what it says.
>
>> * @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
>
> Let's not use "in flight". Perhaps it is better to say,
>
> * @max_submission_credits: number of submission credits this scheduler can hold
> * from all jobs,
>
>> * @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.
>> + *
>> + * This callback is optional.
>> + */
>> + u32 (*update_job_credits)(struct drm_sched_job *sched_job);
>> };
>
> That's good.
>
>>
>> /**
>> @@ -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
>
> Is this clear enough?
>
> I mean, what really is a "submission_limit"? What is it limiting really?
> Number of what? "Submissions"? No. It's credits.
>
> ("Submission" seems to have become very popular, see
> Message-ID: <a39eb381-4f2b-439b-b223-c5148167b225 at amd.com>, maybe through Lore.)
>
> So if "submission_credit_limit" and "submission_credit_count"
> seem too wordy, (and they kind of are), then perhaps use,
>
> @credit_limit: the credit limit of this scheduler
> @credit_count: the current credit count of this scheduler
>
> Also note the slight comment update for those two quantities.
>
>> * @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;
>
> See above. Perhaps "credit_limit" and "credit_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);
>> 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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