[PATCH 6/6] drm/sched: Make use of a "done" thread
Steven Price
steven.price at arm.com
Wed Nov 25 11:09:05 UTC 2020
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.
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.
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 at amd.com>
> ---
> 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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