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drm/sched: Remove FIFO and RR and simplify to a single run queue

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Since the new FAIR policy is in general better than FIFO and almost as
good as round-robin in interactive use cases, plus the latter has not been
the default policy in a long time, we can afford to remove both and leave
just FAIR.

By doing so we can simplify the scheduler code by making the scheduler to
run queue relationship always 1:1 and remove some code.

Also, now that the FIFO policy is gone the tree of entities is not a FIFO
tree any more so rename it to just the tree.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Philipp Stanner <phasta@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Tested-by: Vitaly Prosyak <vitaly.prosyak@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20260417103744.76020-14-tvrtko.ursulin@igalia.com
This commit is contained in:
Tvrtko Ursulin 2026-04-17 11:37:28 +01:00 committed by Philipp Stanner
parent 45c211ddf9
commit 77a6809f1d
6 changed files with 57 additions and 224 deletions
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23
drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
View File

@ -481,25 +481,22 @@ drm_sched_entity_queue_pop(struct drm_sched_entity *entity)
void amdgpu_job_stop_all_jobs_on_sched(struct drm_gpu_scheduler *sched)
{
struct drm_sched_rq *rq = sched->rq;
struct drm_sched_entity *s_entity;
struct drm_sched_job *s_job;
struct drm_sched_entity *s_entity = NULL;
int i;
/* Signal all jobs not yet scheduled */
for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
struct drm_sched_rq *rq = sched->sched_rq[i];
spin_lock(&rq->lock);
list_for_each_entry(s_entity, &rq->entities, list) {
while ((s_job = drm_sched_entity_queue_pop(s_entity))) {
struct drm_sched_fence *s_fence = s_job->s_fence;
spin_lock(&rq->lock);
list_for_each_entry(s_entity, &rq->entities, list) {
while ((s_job = drm_sched_entity_queue_pop(s_entity))) {
struct drm_sched_fence *s_fence = s_job->s_fence;
dma_fence_signal(&s_fence->scheduled);
dma_fence_set_error(&s_fence->finished, -EHWPOISON);
dma_fence_signal(&s_fence->finished);
}
dma_fence_signal(&s_fence->scheduled);
dma_fence_set_error(&s_fence->finished, -EHWPOISON);
dma_fence_signal(&s_fence->finished);
}
spin_unlock(&rq->lock);
}
spin_unlock(&rq->lock);
/* Signal all jobs already scheduled to HW */
list_for_each_entry(s_job, &sched->pending_list, list) {

29
drivers/gpu/drm/scheduler/sched_entity.c
View File

@ -133,37 +133,19 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
entity->guilty = guilty;
entity->priority = priority;
entity->last_user = current->group_leader;
entity->rq_priority = drm_sched_policy == DRM_SCHED_POLICY_FAIR ?
DRM_SCHED_PRIORITY_KERNEL : priority;
entity->num_sched_list = num_sched_list;
entity->sched_list = num_sched_list > 1 ? sched_list : NULL;
RCU_INIT_POINTER(entity->last_scheduled, NULL);
RB_CLEAR_NODE(&entity->rb_tree_node);
if (!sched_list[0]->sched_rq) {
if (!sched_list[0]->rq) {
/* Since every entry covered by num_sched_list
* should be non-NULL and therefore we warn drivers
* not to do this and to fix their DRM calling order.
*/
pr_warn("%s: called with uninitialized scheduler\n", __func__);
} else {
enum drm_sched_priority p = entity->priority;
/*
* The "priority" of an entity cannot exceed the number of
* run-queues of a scheduler. Protect against num_rqs being 0,
* by converting to signed. Choose the lowest priority
* available.
*/
if (p >= sched_list[0]->num_user_rqs) {
dev_err(sched_list[0]->dev, "entity with out-of-bounds priority:%u num_user_rqs:%u\n",
p, sched_list[0]->num_user_rqs);
p = max_t(s32,
(s32)sched_list[0]->num_user_rqs - 1,
(s32)DRM_SCHED_PRIORITY_KERNEL);
entity->priority = p;
}
entity->rq = sched_list[0]->sched_rq[entity->rq_priority];
entity->rq = sched_list[0]->rq;
}
init_completion(&entity->entity_idle);
@ -609,7 +591,7 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity)
spin_lock(&entity->lock);
sched = drm_sched_pick_best(entity->sched_list, entity->num_sched_list);
rq = sched ? sched->sched_rq[entity->rq_priority] : NULL;
rq = sched ? sched->rq : NULL;
if (rq != entity->rq) {
drm_sched_rq_remove_entity(entity->rq, entity);
entity->rq = rq;
@ -634,7 +616,6 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
{
struct drm_sched_entity *entity = sched_job->entity;
bool first;
ktime_t submit_ts;
trace_drm_sched_job_queue(sched_job, entity);
@ -651,16 +632,14 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
/*
* After the sched_job is pushed into the entity queue, it may be
* completed and freed up at any time. We can no longer access it.
* Make sure to set the submit_ts first, to avoid a race.
*/
sched_job->submit_ts = submit_ts = ktime_get();
first = spsc_queue_push(&entity->job_queue, &sched_job->queue_node);
/* first job wakes up scheduler */
if (first) {
struct drm_gpu_scheduler *sched;
sched = drm_sched_rq_add_entity(entity, submit_ts);
sched = drm_sched_rq_add_entity(entity);
if (sched)
drm_sched_wakeup(sched);
}

12
drivers/gpu/drm/scheduler/sched_internal.h
View File

@ -31,13 +31,6 @@ struct drm_sched_entity_stats {
struct ewma_drm_sched_avgtime avg_job_us;
};
/* Used to choose between FIFO and RR job-scheduling */
extern int drm_sched_policy;
#define DRM_SCHED_POLICY_RR 0
#define DRM_SCHED_POLICY_FIFO 1
#define DRM_SCHED_POLICY_FAIR 2
bool drm_sched_can_queue(struct drm_gpu_scheduler *sched,
struct drm_sched_entity *entity);
void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
@ -46,14 +39,13 @@ void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
struct drm_sched_rq *rq);
struct drm_gpu_scheduler *
drm_sched_rq_add_entity(struct drm_sched_entity *entity, ktime_t ts);
drm_sched_rq_add_entity(struct drm_sched_entity *entity);
void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
struct drm_sched_entity *entity);
void drm_sched_rq_pop_entity(struct drm_sched_entity *entity);
struct drm_sched_entity *
drm_sched_rq_select_entity(struct drm_gpu_scheduler *sched,
struct drm_sched_rq *rq);
drm_sched_select_entity(struct drm_gpu_scheduler *sched);
void drm_sched_entity_select_rq(struct drm_sched_entity *entity);
struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity);

108
drivers/gpu/drm/scheduler/sched_main.c
View File

@ -84,15 +84,6 @@
#define CREATE_TRACE_POINTS
#include "gpu_scheduler_trace.h"
int drm_sched_policy = DRM_SCHED_POLICY_FAIR;
/**
* DOC: sched_policy (int)
* Used to override default entities scheduling policy in a run queue.
*/
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, " __stringify(DRM_SCHED_POLICY_FAIR) " = Fair (default).");
module_param_named(sched_policy, drm_sched_policy, int, 0444);
static u32 drm_sched_available_credits(struct drm_gpu_scheduler *sched)
{
u32 credits;
@ -880,34 +871,6 @@ void drm_sched_wakeup(struct drm_gpu_scheduler *sched)
drm_sched_run_job_queue(sched);
}
/**
* drm_sched_select_entity - Select next entity to process
*
* @sched: scheduler instance
*
* Return an entity to process or NULL if none are found.
*
* Note, that we break out of the for-loop when "entity" is non-null, which can
* also be an error-pointer--this assures we don't process lower priority
* run-queues. See comments in the respectively called functions.
*/
static struct drm_sched_entity *
drm_sched_select_entity(struct drm_gpu_scheduler *sched)
{
struct drm_sched_entity *entity = NULL;
int i;
/* Start with the highest priority.
*/
for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
entity = drm_sched_rq_select_entity(sched, sched->sched_rq[i]);
if (entity)
break;
}
return IS_ERR(entity) ? NULL : entity;
}
/**
* drm_sched_get_finished_job - fetch the next finished job to be destroyed
*
@ -1033,7 +996,7 @@ static void drm_sched_run_job_work(struct work_struct *w)
/* Find entity with a ready job */
entity = drm_sched_select_entity(sched);
if (!entity) {
if (IS_ERR_OR_NULL(entity)) {
/*
* Either no more work to do, or the next ready job needs more
* credits than the scheduler has currently available.
@ -1109,8 +1072,6 @@ static struct workqueue_struct *drm_sched_alloc_wq(const char *name)
*/
int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_args *args)
{
int i;
sched->ops = args->ops;
sched->credit_limit = args->credit_limit;
sched->name = args->name;
@ -1120,13 +1081,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_
sched->score = args->score ? args->score : &sched->_score;
sched->dev = args->dev;
if (args->num_rqs > DRM_SCHED_PRIORITY_COUNT) {
/* This is a gross violation--tell drivers what the problem is.
*/
dev_err(sched->dev, "%s: num_rqs cannot be greater than DRM_SCHED_PRIORITY_COUNT\n",
__func__);
return -EINVAL;
} else if (sched->sched_rq) {
if (sched->rq) {
/* Not an error, but warn anyway so drivers can
* fine-tune their DRM calling order, and return all
* is good.
@ -1146,19 +1101,11 @@ int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_
sched->own_submit_wq = true;
}
sched->num_user_rqs = args->num_rqs;
sched->num_rqs = drm_sched_policy != DRM_SCHED_POLICY_FAIR ?
args->num_rqs : 1;
sched->sched_rq = kzalloc_objs(*sched->sched_rq, args->num_rqs);
if (!sched->sched_rq)
sched->rq = kzalloc_obj(*sched->rq);
if (!sched->rq)
goto Out_check_own;
for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
sched->sched_rq[i] = kzalloc_obj(*sched->sched_rq[i]);
if (!sched->sched_rq[i])
goto Out_unroll;
drm_sched_rq_init(sched, sched->sched_rq[i]);
}
drm_sched_rq_init(sched, sched->rq);
init_waitqueue_head(&sched->job_scheduled);
INIT_LIST_HEAD(&sched->pending_list);
@ -1174,12 +1121,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched, const struct drm_sched_init_
sched->ready = true;
return 0;
Out_unroll:
for (--i ; i >= DRM_SCHED_PRIORITY_KERNEL; i--)
kfree(sched->sched_rq[i]);
kfree(sched->sched_rq);
sched->sched_rq = NULL;
Out_check_own:
if (sched->own_submit_wq)
destroy_workqueue(sched->submit_wq);
@ -1215,13 +1157,8 @@ static void drm_sched_cancel_remaining_jobs(struct drm_gpu_scheduler *sched)
*/
void drm_sched_fini(struct drm_gpu_scheduler *sched)
{
int i;
drm_sched_wqueue_stop(sched);
for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++)
kfree(sched->sched_rq[i]);
/* Wakeup everyone stuck in drm_sched_entity_flush for this scheduler */
wake_up_all(&sched->job_scheduled);
@ -1235,8 +1172,8 @@ void drm_sched_fini(struct drm_gpu_scheduler *sched)
if (sched->own_submit_wq)
destroy_workqueue(sched->submit_wq);
sched->ready = false;
kfree(sched->sched_rq);
sched->sched_rq = NULL;
kfree(sched->rq);
sched->rq = NULL;
if (!list_empty(&sched->pending_list))
dev_warn(sched->dev, "Tearing down scheduler while jobs are pending!\n");
@ -1254,35 +1191,28 @@ EXPORT_SYMBOL(drm_sched_fini);
*/
void drm_sched_increase_karma(struct drm_sched_job *bad)
{
int i;
struct drm_sched_entity *tmp;
struct drm_sched_entity *entity;
struct drm_gpu_scheduler *sched = bad->sched;
struct drm_sched_entity *entity, *tmp;
struct drm_sched_rq *rq = sched->rq;
/* don't change @bad's karma if it's from KERNEL RQ,
* because sometimes GPU hang would cause kernel jobs (like VM updating jobs)
* corrupt but keep in mind that kernel jobs always considered good.
*/
if (bad->s_priority != DRM_SCHED_PRIORITY_KERNEL) {
atomic_inc(&bad->karma);
if (bad->s_priority == DRM_SCHED_PRIORITY_KERNEL)
return;
for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
struct drm_sched_rq *rq = sched->sched_rq[i];
atomic_inc(&bad->karma);
spin_lock(&rq->lock);
list_for_each_entry_safe(entity, tmp, &rq->entities, list) {
if (bad->s_fence->scheduled.context ==
entity->fence_context) {
if (entity->guilty)
atomic_set(entity->guilty, 1);
break;
}
}
spin_unlock(&rq->lock);
if (&entity->list != &rq->entities)
break;
spin_lock(&rq->lock);
list_for_each_entry_safe(entity, tmp, &rq->entities, list) {
if (bad->s_fence->scheduled.context == entity->fence_context) {
if (entity->guilty)
atomic_set(entity->guilty, 1);
break;
}
}
spin_unlock(&rq->lock);
}
EXPORT_SYMBOL(drm_sched_increase_karma);

73
drivers/gpu/drm/scheduler/sched_rq.c
View File

@ -49,7 +49,7 @@ static void drm_sched_rq_update_prio(struct drm_sched_rq *rq)
rq->head_prio = prio;
}
static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
static void drm_sched_rq_remove_tree_locked(struct drm_sched_entity *entity,
struct drm_sched_rq *rq)
{
lockdep_assert_held(&entity->lock);
@ -62,7 +62,7 @@ static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
}
}
static void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
static void drm_sched_rq_update_tree_locked(struct drm_sched_entity *entity,
struct drm_sched_rq *rq,
ktime_t ts)
{
@ -74,7 +74,7 @@ static void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
lockdep_assert_held(&entity->lock);
lockdep_assert_held(&rq->lock);
drm_sched_rq_remove_fifo_locked(entity, rq);
drm_sched_rq_remove_tree_locked(entity, rq);
entity->oldest_job_waiting = ts;
@ -239,15 +239,9 @@ static ktime_t drm_sched_entity_update_vruntime(struct drm_sched_entity *entity)
return runtime;
}
static ktime_t drm_sched_entity_get_job_ts(struct drm_sched_entity *entity)
{
return drm_sched_entity_update_vruntime(entity);
}
/**
* drm_sched_rq_add_entity - add an entity
* @entity: scheduler entity
* @ts: submission timestamp
*
* Adds a scheduler entity to the run queue.
*
@ -255,10 +249,11 @@ static ktime_t drm_sched_entity_get_job_ts(struct drm_sched_entity *entity)
* been stopped and cannot be submitted to.
*/
struct drm_gpu_scheduler *
drm_sched_rq_add_entity(struct drm_sched_entity *entity, ktime_t ts)
drm_sched_rq_add_entity(struct drm_sched_entity *entity)
{
struct drm_gpu_scheduler *sched;
struct drm_sched_rq *rq;
ktime_t ts;
/* Add the entity to the run queue */
spin_lock(&entity->lock);
@ -278,15 +273,9 @@ drm_sched_rq_add_entity(struct drm_sched_entity *entity, ktime_t ts)
list_add_tail(&entity->list, &rq->entities);
}
if (drm_sched_policy == DRM_SCHED_POLICY_FAIR) {
ts = drm_sched_rq_get_min_vruntime(rq);
ts = drm_sched_entity_restore_vruntime(entity, ts,
rq->head_prio);
} else if (drm_sched_policy == DRM_SCHED_POLICY_RR) {
ts = entity->rr_ts;
}
drm_sched_rq_update_fifo_locked(entity, rq, ts);
ts = drm_sched_rq_get_min_vruntime(rq);
ts = drm_sched_entity_restore_vruntime(entity, ts, rq->head_prio);
drm_sched_rq_update_tree_locked(entity, rq, ts);
spin_unlock(&rq->lock);
spin_unlock(&entity->lock);
@ -314,27 +303,11 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
atomic_dec(rq->sched->score);
list_del_init(&entity->list);
drm_sched_rq_remove_fifo_locked(entity, rq);
drm_sched_rq_remove_tree_locked(entity, rq);
spin_unlock(&rq->lock);
}
static ktime_t
drm_sched_rq_next_rr_ts(struct drm_sched_rq *rq,
struct drm_sched_entity *entity)
{
ktime_t ts;
lockdep_assert_held(&entity->lock);
lockdep_assert_held(&rq->lock);
ts = ktime_add_ns(rq->rr_ts, 1);
entity->rr_ts = ts;
rq->rr_ts = ts;
return ts;
}
/**
* drm_sched_rq_pop_entity - pops an entity
* @entity: scheduler entity
@ -357,32 +330,22 @@ void drm_sched_rq_pop_entity(struct drm_sched_entity *entity)
if (next_job) {
ktime_t ts;
if (drm_sched_policy == DRM_SCHED_POLICY_FAIR)
ts = drm_sched_entity_get_job_ts(entity);
else if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
ts = next_job->submit_ts;
else
ts = drm_sched_rq_next_rr_ts(rq, entity);
drm_sched_rq_update_fifo_locked(entity, rq, ts);
ts = drm_sched_entity_update_vruntime(entity);
drm_sched_rq_update_tree_locked(entity, rq, ts);
} else {
drm_sched_rq_remove_fifo_locked(entity, rq);
ktime_t min_vruntime;
if (drm_sched_policy == DRM_SCHED_POLICY_FAIR) {
ktime_t min_vruntime;
min_vruntime = drm_sched_rq_get_min_vruntime(rq);
drm_sched_entity_save_vruntime(entity, min_vruntime);
}
drm_sched_rq_remove_tree_locked(entity, rq);
min_vruntime = drm_sched_rq_get_min_vruntime(rq);
drm_sched_entity_save_vruntime(entity, min_vruntime);
}
spin_unlock(&rq->lock);
spin_unlock(&entity->lock);
}
/**
* drm_sched_rq_select_entity - Select an entity which provides a job to run
* drm_sched_select_entity - Select an entity which provides a job to run
* @sched: the gpu scheduler
* @rq: scheduler run queue to check.
*
* Find oldest waiting ready entity.
*
@ -391,9 +354,9 @@ void drm_sched_rq_pop_entity(struct drm_sched_entity *entity)
* its job; return NULL, if no ready entity was found.
*/
struct drm_sched_entity *
drm_sched_rq_select_entity(struct drm_gpu_scheduler *sched,
struct drm_sched_rq *rq)
drm_sched_select_entity(struct drm_gpu_scheduler *sched)
{
struct drm_sched_rq *rq = sched->rq;
struct rb_node *rb;
spin_lock(&rq->lock);

36
include/drm/gpu_scheduler.h
View File

@ -100,8 +100,7 @@ struct drm_sched_entity {
* @lock:
*
* Lock protecting the run-queue (@rq) to which this entity belongs,
* @priority, the list of schedulers (@sched_list, @num_sched_list) and
* the @rr_ts field.
* @priority and the list of schedulers (@sched_list, @num_sched_list).
*/
spinlock_t lock;
@ -154,18 +153,6 @@ struct drm_sched_entity {
*/
enum drm_sched_priority priority;
/**
* @rq_priority: Run-queue priority
*/
enum drm_sched_priority rq_priority;
/**
* @rr_ts:
*
* Fake timestamp of the last popped job from the entity.
*/
ktime_t rr_ts;
/**
* @job_queue: the list of jobs of this entity.
*/
@ -263,8 +250,7 @@ struct drm_sched_entity {
* struct drm_sched_rq - queue of entities to be scheduled.
*
* @sched: the scheduler to which this rq belongs to.
* @lock: protects @entities, @rb_tree_root, @rr_ts and @head_prio.
* @rr_ts: monotonically incrementing fake timestamp for RR mode.
* @lock: protects @entities, @rb_tree_root and @head_prio.
* @entities: list of the entities to be scheduled.
* @rb_tree_root: root of time based priority queue of entities for FIFO scheduling
* @head_prio: priority of the top tree element.
@ -278,7 +264,6 @@ struct drm_sched_rq {
spinlock_t lock;
/* Following members are protected by the @lock: */
ktime_t rr_ts;
struct list_head entities;
struct rb_root_cached rb_tree_root;
enum drm_sched_priority head_prio;
@ -364,13 +349,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
* to schedule the job.
*/
struct drm_sched_job {
/**
* @submit_ts:
*
* When the job was pushed into the entity queue.
*/
ktime_t submit_ts;
/**
* @sched:
*
@ -574,11 +552,7 @@ struct drm_sched_backend_ops {
* @credit_count: the current credit count of this scheduler
* @timeout: the time after which a job is removed from the scheduler.
* @name: name of the ring for which this scheduler is being used.
* @num_user_rqs: Number of run-queues. This is at most
* DRM_SCHED_PRIORITY_COUNT, as there's usually one run-queue per
* priority, but could be less.
* @num_rqs: Equal to @num_user_rqs for FIFO and RR and 1 for the FAIR policy.
* @sched_rq: An allocated array of run-queues of size @num_rqs;
* @rq: Scheduler run queue.
* @job_scheduled: once drm_sched_entity_flush() is called the scheduler
* waits on this wait queue until all the scheduled jobs are
* finished.
@ -610,9 +584,7 @@ struct drm_gpu_scheduler {
atomic_t credit_count;
long timeout;
const char *name;
u32 num_rqs;
u32 num_user_rqs;
struct drm_sched_rq **sched_rq;
struct drm_sched_rq *rq;
wait_queue_head_t job_scheduled;
atomic64_t job_id_count;
struct workqueue_struct *submit_wq;