[Intel-gfx] [RFC PATCH 04/20] drm/sched: Convert drm scheduler to use a work queue rather than kthread
Rob Clark
robdclark at gmail.com
Fri Dec 23 17:42:58 UTC 2022
On Thu, Dec 22, 2022 at 2:29 PM Matthew Brost <matthew.brost at intel.com> 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.
You might want to enable CONFIG_DRM_MSM in your kconfig, I think you
missed a part
BR,
-R
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 14 +--
> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 12 +-
> drivers/gpu/drm/scheduler/sched_main.c | 124 ++++++++++++--------
> include/drm/gpu_scheduler.h | 13 +-
> 4 files changed, 93 insertions(+), 70 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> index f60753f97ac5..9c2a10aeb0b3 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
> @@ -1489,9 +1489,9 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused)
> for (i = 0; i < AMDGPU_MAX_RINGS; i++) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
> - kthread_park(ring->sched.thread);
> + drm_sched_run_wq_stop(&ring->sched);
> }
>
> seq_printf(m, "run ib test:\n");
> @@ -1505,9 +1505,9 @@ static int amdgpu_debugfs_test_ib_show(struct seq_file *m, void *unused)
> for (i = 0; i < AMDGPU_MAX_RINGS; i++) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
> - kthread_unpark(ring->sched.thread);
> + drm_sched_run_wq_start(&ring->sched);
> }
>
> up_write(&adev->reset_domain->sem);
> @@ -1727,7 +1727,7 @@ static int amdgpu_debugfs_ib_preempt(void *data, u64 val)
>
> ring = adev->rings[val];
>
> - if (!ring || !ring->funcs->preempt_ib || !ring->sched.thread)
> + if (!ring || !ring->funcs->preempt_ib || !ring->sched.ready)
> return -EINVAL;
>
> /* the last preemption failed */
> @@ -1745,7 +1745,7 @@ static int amdgpu_debugfs_ib_preempt(void *data, u64 val)
> goto pro_end;
>
> /* stop the scheduler */
> - kthread_park(ring->sched.thread);
> + drm_sched_run_wq_stop(&ring->sched);
>
> /* preempt the IB */
> r = amdgpu_ring_preempt_ib(ring);
> @@ -1779,7 +1779,7 @@ static int amdgpu_debugfs_ib_preempt(void *data, u64 val)
>
> failure:
> /* restart the scheduler */
> - kthread_unpark(ring->sched.thread);
> + drm_sched_run_wq_start(&ring->sched);
>
> up_read(&adev->reset_domain->sem);
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 076ae400d099..9552929ccf87 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -4577,7 +4577,7 @@ bool amdgpu_device_has_job_running(struct amdgpu_device *adev)
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> spin_lock(&ring->sched.job_list_lock);
> @@ -4708,7 +4708,7 @@ int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> /*clear job fence from fence drv to avoid force_completion
> @@ -5247,7 +5247,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = tmp_adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> drm_sched_stop(&ring->sched, job ? &job->base : NULL);
> @@ -5321,7 +5321,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = tmp_adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> drm_sched_start(&ring->sched, true);
> @@ -5648,7 +5648,7 @@ pci_ers_result_t amdgpu_pci_error_detected(struct pci_dev *pdev, pci_channel_sta
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> drm_sched_stop(&ring->sched, NULL);
> @@ -5776,7 +5776,7 @@ void amdgpu_pci_resume(struct pci_dev *pdev)
> for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
> struct amdgpu_ring *ring = adev->rings[i];
>
> - if (!ring || !ring->sched.thread)
> + if (!ring || !ring->sched.ready)
> continue;
>
> drm_sched_start(&ring->sched, true);
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 27d52ffbb808..8c64045d0692 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -44,7 +44,6 @@
> * The jobs in a entity are always scheduled in the order that they were pushed.
> */
>
> -#include <linux/kthread.h>
> #include <linux/wait.h>
> #include <linux/sched.h>
> #include <linux/completion.h>
> @@ -251,6 +250,53 @@ 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_run_wq_stop - stop scheduler run worker
> + *
> + * @sched: scheduler instance to stop run worker
> + */
> +void drm_sched_run_wq_stop(struct drm_gpu_scheduler *sched)
> +{
> + sched->pause_run_wq = true;
> + smp_wmb();
> +
> + cancel_work_sync(&sched->work_run);
> +}
> +EXPORT_SYMBOL(drm_sched_run_wq_stop);
> +
> +/**
> + * drm_sched_run_wq_start - start scheduler run worker
> + *
> + * @sched: scheduler instance to start run worker
> + */
> +void drm_sched_run_wq_start(struct drm_gpu_scheduler *sched)
> +{
> + sched->pause_run_wq = false;
> + smp_wmb();
> +
> + queue_work(sched->run_wq, &sched->work_run);
> +}
> +EXPORT_SYMBOL(drm_sched_run_wq_start);
> +
> +/**
> + * drm_sched_run_wq_queue - queue scheduler run worker
> + *
> + * @sched: scheduler instance to queue run worker
> + */
> +static void drm_sched_run_wq_queue(struct drm_gpu_scheduler *sched)
> +{
> + smp_rmb();
> +
> + /*
> + * Try not to schedule work if pause_run_wq set but not the end of world
> + * if we do as either it will be cancelled by the above
> + * cancel_work_sync, or drm_sched_main turns into a NOP while
> + * pause_run_wq is set.
> + */
> + if (!sched->pause_run_wq)
> + queue_work(sched->run_wq, &sched->work_run);
> +}
> +
> /**
> * drm_sched_job_done - complete a job
> * @s_job: pointer to the job which is done
> @@ -270,7 +316,7 @@ 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);
> + drm_sched_run_wq_queue(sched);
> }
>
> /**
> @@ -433,7 +479,7 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
> {
> struct drm_sched_job *s_job, *tmp;
>
> - kthread_park(sched->thread);
> + drm_sched_run_wq_stop(sched);
>
> /*
> * Reinsert back the bad job here - now it's safe as
> @@ -546,7 +592,7 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
> spin_unlock(&sched->job_list_lock);
> }
>
> - kthread_unpark(sched->thread);
> + drm_sched_run_wq_start(sched);
> }
> EXPORT_SYMBOL(drm_sched_start);
>
> @@ -831,7 +877,7 @@ static bool drm_sched_ready(struct drm_gpu_scheduler *sched)
> void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
> {
> if (drm_sched_ready(sched))
> - wake_up_interruptible(&sched->wake_up_worker);
> + drm_sched_run_wq_queue(sched);
> }
>
> /**
> @@ -941,60 +987,42 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
> }
> EXPORT_SYMBOL(drm_sched_pick_best);
>
> -/**
> - * drm_sched_blocked - check if the scheduler is blocked
> - *
> - * @sched: scheduler instance
> - *
> - * Returns true if blocked, otherwise false.
> - */
> -static bool drm_sched_blocked(struct drm_gpu_scheduler *sched)
> -{
> - if (kthread_should_park()) {
> - kthread_parkme();
> - return true;
> - }
> -
> - return false;
> -}
> -
> /**
> * drm_sched_main - main scheduler thread
> *
> * @param: scheduler instance
> - *
> - * Returns 0.
> */
> -static int drm_sched_main(void *param)
> +static void drm_sched_main(struct work_struct *w)
> {
> - struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
> + struct drm_gpu_scheduler *sched =
> + container_of(w, struct drm_gpu_scheduler, work_run);
> int r;
>
> - sched_set_fifo_low(current);
> -
> - while (!kthread_should_stop()) {
> - struct drm_sched_entity *entity = NULL;
> + while (!READ_ONCE(sched->pause_run_wq)) {
> + struct drm_sched_entity *entity;
> struct drm_sched_fence *s_fence;
> struct drm_sched_job *sched_job;
> struct dma_fence *fence;
> - struct drm_sched_job *cleanup_job = NULL;
> + struct drm_sched_job *cleanup_job;
>
> - 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());
> + cleanup_job = drm_sched_get_cleanup_job(sched);
> + entity = drm_sched_select_entity(sched);
>
> if (cleanup_job)
> sched->ops->free_job(cleanup_job);
>
> - if (!entity)
> + if (!entity) {
> + if (!cleanup_job)
> + break;
> continue;
> + }
>
> sched_job = drm_sched_entity_pop_job(entity);
>
> if (!sched_job) {
> complete_all(&entity->entity_idle);
> + if (!cleanup_job)
> + break;
> continue;
> }
>
> @@ -1022,14 +1050,14 @@ static int drm_sched_main(void *param)
> r);
> } else {
> if (IS_ERR(fence))
> - dma_fence_set_error(&s_fence->finished, PTR_ERR(fence));
> + dma_fence_set_error(&s_fence->finished,
> + PTR_ERR(fence));
>
> drm_sched_job_done(sched_job);
> }
>
> wake_up(&sched->job_scheduled);
> }
> - return 0;
> }
>
> /**
> @@ -1054,35 +1082,28 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
> long timeout, struct workqueue_struct *timeout_wq,
> atomic_t *score, const char *name, struct device *dev)
> {
> - int i, ret;
> + int i;
> sched->ops = ops;
> sched->hw_submission_limit = hw_submission;
> sched->name = name;
> sched->timeout = timeout;
> sched->timeout_wq = timeout_wq ? : system_wq;
> + sched->run_wq = system_wq; /* FIXME: Let user pass this in */
> sched->hang_limit = hang_limit;
> sched->score = score ? score : &sched->_score;
> sched->dev = dev;
> for (i = DRM_SCHED_PRIORITY_MIN; i < DRM_SCHED_PRIORITY_COUNT; i++)
> drm_sched_rq_init(sched, &sched->sched_rq[i]);
>
> - init_waitqueue_head(&sched->wake_up_worker);
> 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);
> INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
> + INIT_WORK(&sched->work_run, drm_sched_main);
> atomic_set(&sched->_score, 0);
> atomic64_set(&sched->job_id_count, 0);
> -
> - /* Each scheduler will run on a seperate kernel thread */
> - sched->thread = kthread_run(drm_sched_main, sched, sched->name);
> - if (IS_ERR(sched->thread)) {
> - ret = PTR_ERR(sched->thread);
> - sched->thread = NULL;
> - DRM_DEV_ERROR(sched->dev, "Failed to create scheduler for %s.\n", name);
> - return ret;
> - }
> + sched->pause_run_wq = false;
>
> sched->ready = true;
> return 0;
> @@ -1101,8 +1122,7 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
> struct drm_sched_entity *s_entity;
> int i;
>
> - if (sched->thread)
> - kthread_stop(sched->thread);
> + drm_sched_run_wq_stop(sched);
>
> for (i = DRM_SCHED_PRIORITY_COUNT - 1; i >= DRM_SCHED_PRIORITY_MIN; i--) {
> struct drm_sched_rq *rq = &sched->sched_rq[i];
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index ca857ec9e7eb..ff50f3c289cd 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -456,17 +456,16 @@ struct drm_sched_backend_ops {
> * @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.
> - * @wake_up_worker: the wait queue on which the scheduler sleeps until a job
> - * is ready to be scheduled.
> * @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.
> + * @run_wq: workqueue used to queue @work_run
> * @timeout_wq: workqueue used to queue @work_tdr
> + * @work_run: schedules jobs and cleans up entities
> * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
> * timeout interval is over.
> - * @thread: the kthread on which the scheduler which run.
> * @pending_list: the list of jobs which are currently in the job queue.
> * @job_list_lock: lock to protect the pending_list.
> * @hang_limit: once the hangs by a job crosses this limit then it is marked
> @@ -475,6 +474,7 @@ struct drm_sched_backend_ops {
> * @_score: score used when the driver doesn't provide one
> * @ready: marks if the underlying HW is ready to work
> * @free_guilty: A hit to time out handler to free the guilty job.
> + * @pause_run_wq: pause queuing of @work_run on @run_wq
> * @dev: system &struct device
> *
> * One scheduler is implemented for each hardware ring.
> @@ -485,13 +485,13 @@ struct drm_gpu_scheduler {
> long timeout;
> const char *name;
> struct drm_sched_rq sched_rq[DRM_SCHED_PRIORITY_COUNT];
> - wait_queue_head_t wake_up_worker;
> wait_queue_head_t job_scheduled;
> atomic_t hw_rq_count;
> atomic64_t job_id_count;
> + struct workqueue_struct *run_wq;
> struct workqueue_struct *timeout_wq;
> + struct work_struct work_run;
> struct delayed_work work_tdr;
> - struct task_struct *thread;
> struct list_head pending_list;
> spinlock_t job_list_lock;
> int hang_limit;
> @@ -499,6 +499,7 @@ struct drm_gpu_scheduler {
> atomic_t _score;
> bool ready;
> bool free_guilty;
> + bool pause_run_wq;
> struct device *dev;
> };
>
> @@ -529,6 +530,8 @@ void drm_sched_entity_modify_sched(struct drm_sched_entity *entity,
>
> void drm_sched_job_cleanup(struct drm_sched_job *job);
> void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
> +void drm_sched_run_wq_stop(struct drm_gpu_scheduler *sched);
> +void drm_sched_run_wq_start(struct drm_gpu_scheduler *sched);
> void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad);
> void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery);
> void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched);
> --
> 2.37.3
>
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