On 2020-11-25 06:09, Steven Price wrote:
> On 25/11/2020 03:17, Luben Tuikov wrote:
>> Add a "done" list to which all completed jobs are added
>> to be freed. The drm_sched_job_done() callback is the
>> producer of jobs to this list.
>>
>> Add a "done" thread which consumes from the done list
>> and frees up jobs. Now, the main scheduler thread only
>> pushes jobs to the GPU and the "done" thread frees them
>> up, on the way out of the GPU when they've completed
>> execution.
>
> Generally I'd be in favour of a "done thread" as I think there are some
> murky corners of Panfrost's locking that would be helped by deferring
> the free_job() callback.
Check my response to his email.
It seems you're okay with a separate thread, when both threads
could be working concurrently, and Christian wants
a single thread doing all this. You should probably address
this in a follow-up to his email, so this can be hashed out.
>
> But I think you're trying to do too much in one patch here. And as
> Christian has pointed out there's some dodgy looking changes to locking
> which aren't explained.
I've addressed this in my response to his email, check it out.
So, if you're in favour of a separate thread working concurrently,
please follow up to his email, so this can be hashed out.
Thanks and Regards,
Luben
>
> Steve
>
>>
>> Make use of the status returned by the GPU driver
>> timeout handler to decide whether to leave the job in
>> the pending list, or to send it off to the done list.
>> If a job is done, it is added to the done list and the
>> done thread woken up. If a job needs more time, it is
>> left on the pending list and the timeout timer
>> restarted.
>>
>> Eliminate the polling mechanism of picking out done
>> jobs from the pending list, i.e. eliminate
>> drm_sched_get_cleanup_job(). Now the main scheduler
>> thread only pushes jobs down to the GPU.
>>
>> Various other optimizations to the GPU scheduler
>> and job recovery are possible with this format.
>>
>> Signed-off-by: Luben Tuikov <luben.tuikov@xxxxxxx>
>> ---
>> drivers/gpu/drm/scheduler/sched_main.c | 173 +++++++++++++------------
>> include/drm/gpu_scheduler.h | 14 ++
>> 2 files changed, 101 insertions(+), 86 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
>> index 3eb7618a627d..289ae68cd97f 100644
>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>> @@ -164,7 +164,8 @@ drm_sched_rq_select_entity(struct drm_sched_rq *rq)
>> * drm_sched_job_done - complete a job
>> * @s_job: pointer to the job which is done
>> *
>> - * Finish the job's fence and wake up the worker thread.
>> + * Finish the job's fence, move it to the done list,
>> + * and wake up the done thread.
>> */
>> static void drm_sched_job_done(struct drm_sched_job *s_job)
>> {
>> @@ -179,7 +180,12 @@ static void drm_sched_job_done(struct drm_sched_job *s_job)
>> dma_fence_get(&s_fence->finished);
>> drm_sched_fence_finished(s_fence);
>> dma_fence_put(&s_fence->finished);
>> - wake_up_interruptible(&sched->wake_up_worker);
>> +
>> + spin_lock(&sched->job_list_lock);
>> + list_move(&s_job->list, &sched->done_list);
>> + spin_unlock(&sched->job_list_lock);
>> +
>> + wake_up_interruptible(&sched->done_wait_q);
>> }
>>
>> /**
>> @@ -221,11 +227,10 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,
>> EXPORT_SYMBOL(drm_sched_dependency_optimized);
>>
>> /**
>> - * drm_sched_start_timeout - start timeout for reset worker
>> - *
>> - * @sched: scheduler instance to start the worker for
>> + * drm_sched_start_timeout - start a timeout timer
>> + * @sched: scheduler instance whose job we're timing
>> *
>> - * Start the timeout for the given scheduler.
>> + * Start a timeout timer for the given scheduler.
>> */
>> static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
>> {
>> @@ -305,8 +310,8 @@ static void drm_sched_job_begin(struct drm_sched_job *s_job)
>>
>> spin_lock(&sched->job_list_lock);
>> list_add_tail(&s_job->list, &sched->pending_list);
>> - drm_sched_start_timeout(sched);
>> spin_unlock(&sched->job_list_lock);
>> + drm_sched_start_timeout(sched);
>> }
>>
>> static void drm_sched_job_timedout(struct work_struct *work)
>> @@ -316,37 +321,30 @@ static void drm_sched_job_timedout(struct work_struct *work)
>>
>> sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);
>>
>> - /* Protects against concurrent deletion in drm_sched_get_cleanup_job */
>> spin_lock(&sched->job_list_lock);
>> job = list_first_entry_or_null(&sched->pending_list,
>> struct drm_sched_job, list);
>> + spin_unlock(&sched->job_list_lock);
>>
>> if (job) {
>> - /*
>> - * Remove the bad job so it cannot be freed by concurrent
>> - * drm_sched_cleanup_jobs. It will be reinserted back after sched->thread
>> - * is parked at which point it's safe.
>> - */
>> - list_del_init(&job->list);
>> - spin_unlock(&sched->job_list_lock);
>> + int res;
>>
>> - job->sched->ops->timedout_job(job);
>> + job->job_status |= DRM_JOB_STATUS_TIMEOUT;
>> + res = job->sched->ops->timedout_job(job);
>> + if (res == 0) {
>> + /* The job is out of the device.
>> + */
>> + spin_lock(&sched->job_list_lock);
>> + list_move(&job->list, &sched->done_list);
>> + spin_unlock(&sched->job_list_lock);
>>
>> - /*
>> - * Guilty job did complete and hence needs to be manually removed
>> - * See drm_sched_stop doc.
>> - */
>> - if (sched->free_guilty) {
>> - job->sched->ops->free_job(job);
>> - sched->free_guilty = false;
>> + wake_up_interruptible(&sched->done_wait_q);
>> + } else {
>> + /* The job needs more time.
>> + */
>> + drm_sched_start_timeout(sched);
>> }
>> - } else {
>> - spin_unlock(&sched->job_list_lock);
>> }
>> -
>> - spin_lock(&sched->job_list_lock);
>> - drm_sched_start_timeout(sched);
>> - spin_unlock(&sched->job_list_lock);
>> }
>>
>> /**
>> @@ -511,15 +509,13 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
>> else if (r)
>> DRM_ERROR("fence add callback failed (%d)\n",
>> r);
>> - } else
>> + } else {
>> drm_sched_job_done(s_job);
>> + }
>> }
>>
>> - if (full_recovery) {
>> - spin_lock(&sched->job_list_lock);
>> + if (full_recovery)
>> drm_sched_start_timeout(sched);
>> - spin_unlock(&sched->job_list_lock);
>> - }
>>
>> kthread_unpark(sched->thread);
>> }
>> @@ -667,47 +663,6 @@ drm_sched_select_entity(struct drm_gpu_scheduler *sched)
>> return entity;
>> }
>>
>> -/**
>> - * drm_sched_get_cleanup_job - fetch the next finished job to be destroyed
>> - *
>> - * @sched: scheduler instance
>> - *
>> - * Returns the next finished job from the pending list (if there is one)
>> - * ready for it to be destroyed.
>> - */
>> -static struct drm_sched_job *
>> -drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>> -{
>> - struct drm_sched_job *job;
>> -
>> - /*
>> - * Don't destroy jobs while the timeout worker is running OR thread
>> - * is being parked and hence assumed to not touch pending_list
>> - */
>> - if ((sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>> - !cancel_delayed_work(&sched->work_tdr)) ||
>> - kthread_should_park())
>> - return NULL;
>> -
>> - spin_lock(&sched->job_list_lock);
>> -
>> - job = list_first_entry_or_null(&sched->pending_list,
>> - struct drm_sched_job, list);
>> -
>> - if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
>> - /* remove job from pending_list */
>> - list_del_init(&job->list);
>> - } else {
>> - job = NULL;
>> - /* queue timeout for next job */
>> - drm_sched_start_timeout(sched);
>> - }
>> -
>> - spin_unlock(&sched->job_list_lock);
>> -
>> - return job;
>> -}
>> -
>> /**
>> * drm_sched_pick_best - Get a drm sched from a sched_list with the least load
>> * @sched_list: list of drm_gpu_schedulers
>> @@ -761,6 +716,44 @@ static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
>> return false;
>> }
>>
>> +/**
>> + * drm_sched_done - free done tasks
>> + * @param: pointer to a scheduler instance
>> + *
>> + * Returns 0.
>> + */
>> +static int drm_sched_done(void *param)
>> +{
>> + struct drm_gpu_scheduler *sched = param;
>> +
>> + do {
>> + LIST_HEAD(done_q);
>> +
>> + wait_event_interruptible(sched->done_wait_q,
>> + kthread_should_stop() ||
>> + !list_empty(&sched->done_list));
>> +
>> + spin_lock(&sched->job_list_lock);
>> + list_splice_init(&sched->done_list, &done_q);
>> + spin_unlock(&sched->job_list_lock);
>> +
>> + if (list_empty(&done_q))
>> + continue;
>> +
>> + while (!list_empty(&done_q)) {
>> + struct drm_sched_job *job;
>> +
>> + job = list_first_entry(&done_q,
>> + struct drm_sched_job,
>> + list);
>> + list_del_init(&job->list);
>> + sched->ops->free_job(job);
>> + }
>> + } while (!kthread_should_stop());
>> +
>> + return 0;
>> +}
>> +
>> /**
>> * drm_sched_main - main scheduler thread
>> *
>> @@ -770,7 +763,7 @@ static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
>> */
>> static int drm_sched_main(void *param)
>> {
>> - struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
>> + struct drm_gpu_scheduler *sched = param;
>> int r;
>>
>> sched_set_fifo_low(current);
>> @@ -780,20 +773,12 @@ static int drm_sched_main(void *param)
>> struct drm_sched_fence *s_fence;
>> struct drm_sched_job *sched_job;
>> struct dma_fence *fence;
>> - struct drm_sched_job *cleanup_job = NULL;
>>
>> wait_event_interruptible(sched->wake_up_worker,
>> - (cleanup_job = drm_sched_get_cleanup_job(sched)) ||
>> (!drm_sched_blocked(sched) &&
>> (entity = drm_sched_select_entity(sched))) ||
>> kthread_should_stop());
>>
>> - if (cleanup_job) {
>> - sched->ops->free_job(cleanup_job);
>> - /* queue timeout for next job */
>> - drm_sched_start_timeout(sched);
>> - }
>> -
>> if (!entity)
>> continue;
>>
>> @@ -820,8 +805,7 @@ static int drm_sched_main(void *param)
>> if (r == -ENOENT)
>> drm_sched_job_done(sched_job);
>> else if (r)
>> - DRM_ERROR("fence add callback failed (%d)\n",
>> - r);
>> + DRM_ERROR("fence add callback failed (%d)\n", r);
>> dma_fence_put(fence);
>> } else {
>> if (IS_ERR(fence))
>> @@ -865,7 +849,9 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
>>
>> init_waitqueue_head(&sched->wake_up_worker);
>> init_waitqueue_head(&sched->job_scheduled);
>> + init_waitqueue_head(&sched->done_wait_q);
>> INIT_LIST_HEAD(&sched->pending_list);
>> + INIT_LIST_HEAD(&sched->done_list);
>> spin_lock_init(&sched->job_list_lock);
>> atomic_set(&sched->hw_rq_count, 0);
>> INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
>> @@ -881,6 +867,21 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
>> return ret;
>> }
>>
>> + snprintf(sched->thread_done_name, DRM_THREAD_NAME_LEN, "%s%s",
>> + sched->name, "-done");
>> + sched->thread_done_name[DRM_THREAD_NAME_LEN - 1] = '\0';
>> + sched->thread_done = kthread_run(drm_sched_done, sched,
>> + sched->thread_done_name);
>> + if (IS_ERR(sched->thread_done)) {
>> + ret = kthread_stop(sched->thread);
>> + if (!ret) {
>> + /* free_kthread_struct(sched->thread); */
>> + sched->thread = NULL;
>> + }
>> + DRM_ERROR("Failed to start thread %s", sched->thread_done_name);
>> + return ret;
>> + }
>> +
>> sched->ready = true;
>> return 0;
>> }
>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>> index 3a5686c3b5e9..b282d6158b50 100644
>> --- a/include/drm/gpu_scheduler.h
>> +++ b/include/drm/gpu_scheduler.h
>> @@ -169,6 +169,12 @@ struct drm_sched_fence {
>>
>> struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>>
>> +enum drm_job_status {
>> + DRM_JOB_STATUS_NONE = 0 << 0,
>> + DRM_JOB_STATUS_DONE = 1 << 0,
>> + DRM_JOB_STATUS_TIMEOUT = 1 << 1,
>> +};
>> +
>> /**
>> * struct drm_sched_job - A job to be run by an entity.
>> *
>> @@ -198,6 +204,7 @@ struct drm_sched_job {
>> uint64_t id;
>> atomic_t karma;
>> enum drm_sched_priority s_priority;
>> + enum drm_job_status job_status;
>> struct drm_sched_entity *entity;
>> struct dma_fence_cb cb;
>> };
>> @@ -284,15 +291,22 @@ struct drm_gpu_scheduler {
>> uint32_t hw_submission_limit;
>> long timeout;
>> const char *name;
>> + char thread_done_name[DRM_THREAD_NAME_LEN];
>> +
>> struct drm_sched_rq sched_rq[DRM_SCHED_PRIORITY_COUNT];
>> wait_queue_head_t wake_up_worker;
>> wait_queue_head_t job_scheduled;
>> + wait_queue_head_t done_wait_q;
>> atomic_t hw_rq_count;
>> atomic64_t job_id_count;
>> struct delayed_work work_tdr;
>> struct task_struct *thread;
>> + struct task_struct *thread_done;
>> +
>> struct list_head pending_list;
>> + struct list_head done_list;
>> spinlock_t job_list_lock;
>> +
>> int hang_limit;
>> atomic_t score;
>> bool ready;
>>
>
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