On to, 2016-02-18 at 14:27 +0000, John.C.Harrison@xxxxxxxxx wrote:
> From: John Harrison <John.C.Harrison@xxxxxxxxx>
>
> When requesting that all GPU work is completed, it is now necessary to
> get the scheduler involved in order to flush out work that queued and
> not yet submitted.
>
> v2: Updated to add support for flushing the scheduler queue by time
> stamp rather than just doing a blanket flush.
>
> v3: Moved submit_max_priority() to this patch from an earlier patch
> is it is no longer required in the other.
>
> v4: Corrected the format of a comment to keep the style checker happy.
> Downgraded a BUG_ON to a WARN_ON as the latter is preferred.
>
> v5: Shuffled functions around to remove forward prototypes, removed
> similarly offensive white space and added documentation. Re-worked the
> mutex locking around the submit function. [Joonas Lahtinen]
>
> Used lighter weight spinlocks.
>
> For: VIZ-1587
> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 24 ++++-
> drivers/gpu/drm/i915/i915_scheduler.c | 178 ++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/i915_scheduler.h | 3 +
> 3 files changed, 204 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index a47a495..d946f53 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -3786,6 +3786,10 @@ int i915_gpu_idle(struct drm_device *dev)
>
> /* Flush everything onto the inactive list. */
> for_each_ring(ring, dev_priv, i) {
> + ret = i915_scheduler_flush(ring, true);
> + if (ret < 0)
> + return ret;
> +
> if (!i915.enable_execlists) {
> struct drm_i915_gem_request *req;
>
> @@ -4519,7 +4523,8 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
> unsigned long recent_enough = jiffies - DRM_I915_THROTTLE_JIFFIES;
> struct drm_i915_gem_request *request, *target = NULL;
> unsigned reset_counter;
> - int ret;
> + int i, ret;
> + struct intel_engine_cs *ring;
>
> ret = i915_gem_wait_for_error(&dev_priv->gpu_error);
> if (ret)
> @@ -4529,6 +4534,23 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
> if (ret)
> return ret;
>
> + for_each_ring(ring, dev_priv, i) {
> + /*
> + * Flush out scheduler entries that are getting 'stale'. Note
> + * that the following recent_enough test will only check
> + * against the time at which the request was submitted to the
> + * hardware (i.e. when it left the scheduler) not the time it
> + * was submitted to the driver.
> + *
> + * Also, there is not much point worring about busy return
> + * codes from the scheduler flush call. Even if more work
> + * cannot be submitted right now for whatever reason, we
> + * still want to throttle against stale work that has already
> + * been submitted.
> + */
> + i915_scheduler_flush_stamp(ring, recent_enough, false);
> + }
> +
> spin_lock(&file_priv->mm.lock);
> list_for_each_entry(request, &file_priv->mm.request_list, client_list) {
> if (time_after_eq(request->emitted_jiffies, recent_enough))
> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
> index edab63d..8130a9c 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler.c
> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
> @@ -304,6 +304,10 @@ static int i915_scheduler_pop_from_queue_locked(struct intel_engine_cs *ring,
> * attempting to acquire a mutex while holding a spin lock is a Bad Idea.
> * And releasing the one before acquiring the other leads to other code
> * being run and interfering.
> + *
> + * Hence any caller that does not already have the mutex lock for other
> + * reasons should call i915_scheduler_submit_unlocked() instead in order to
> + * obtain the lock first.
> */
> static int i915_scheduler_submit(struct intel_engine_cs *ring)
> {
> @@ -428,6 +432,22 @@ error:
> return ret;
> }
>
> +static int i915_scheduler_submit_unlocked(struct intel_engine_cs *ring)
> +{
> + struct drm_device *dev = ring->dev;
> + int ret;
> +
> + ret = i915_mutex_lock_interruptible(dev);
> + if (ret)
> + return ret;
> +
> + ret = i915_scheduler_submit(ring);
> +
> + mutex_unlock(&dev->struct_mutex);
> +
> + return ret;
> +}
> +
This kind of code should really be factored to upper level functions.
> static void i915_generate_dependencies(struct i915_scheduler *scheduler,
> struct i915_scheduler_queue_entry *node,
> uint32_t ring)
> @@ -917,6 +937,164 @@ void i915_scheduler_work_handler(struct work_struct *work)
> i915_scheduler_process_work(ring);
> }
>
> +static int i915_scheduler_submit_max_priority(struct intel_engine_cs *ring,
> + bool is_locked)
> +{
> + struct i915_scheduler_queue_entry *node;
> + struct drm_i915_private *dev_priv = ring->dev->dev_private;
> + struct i915_scheduler *scheduler = dev_priv->scheduler;
> + int ret, count = 0;
> + bool found;
> +
> + do {
> + found = false;
> + spin_lock_irq(&scheduler->lock);
> + list_for_each_entry(node, &scheduler->node_queue[ring->id], link) {
> + if (!I915_SQS_IS_QUEUED(node))
> + continue;
> +
> + if (node->priority < scheduler->priority_level_max)
> + continue;
> +
> + found = true;
> + break;
> + }
> + spin_unlock_irq(&scheduler->lock);
> +
> + if (!found)
> + break;
> +
> + if (is_locked)
> + ret = i915_scheduler_submit(ring);
> + else
> + ret = i915_scheduler_submit_unlocked(ring);
The widespread use of 'is_locked' notation is really bothering me, I
think the difference in code path should be handled in the upper level,
instead of being passed down, for example this will cause repetitive
lock/unlock in loop.
> + if (ret < 0)
> + return ret;
> +
> + count += ret;
> + } while (found);
> +
> + return count;
> +}
> +
> +/**
> + * i915_scheduler_flush_stamp - force requests of a given age through the
> + * scheduler.
> + * @ring: Ring to be flushed
> + * @target: Jiffy based time stamp to flush up to
> + * @is_locked: Is the driver mutex lock held?
> + * DRM has a throttle by age of request facility. This requires waiting for
> + * outstanding work over a given age. This function helps that by forcing
> + * queued batch buffers over said age through the system.
> + * Returns zero on success or -EAGAIN if the scheduler is busy (e.g. waiting
> + * for a pre-emption event to complete) but the mutex lock is held which
> + * would prevent the scheduler's asynchronous processing from completing.
> + */
> +int i915_scheduler_flush_stamp(struct intel_engine_cs *ring,
> + unsigned long target,
> + bool is_locked)
> +{
> + struct i915_scheduler_queue_entry *node;
> + struct drm_i915_private *dev_priv;
> + struct i915_scheduler *scheduler;
> + int flush_count = 0;
> +
> + if (!ring)
> + return -EINVAL;
> +
> + dev_priv = ring->dev->dev_private;
> + scheduler = dev_priv->scheduler;
> +
> + if (!scheduler)
> + return 0;
> +
> + if (is_locked && (scheduler->flags[ring->id] & i915_sf_submitting)) {
> + /*
> + * Scheduler is busy already submitting another batch,
> + * come back later rather than going recursive...
> + */
> + return -EAGAIN;
> + }
> +
Again, this would be handled better at higher level.
So I would like to see those 'is_locked' and other similar constructs
factored out from the series. It should make the code much more robust
to modify at later point.
Regards, Joonas
> + spin_lock_irq(&scheduler->lock);
> + i915_scheduler_priority_bump_clear(scheduler);
> + list_for_each_entry(node, &scheduler->node_queue[ring->id], link) {
> + if (!I915_SQS_IS_QUEUED(node))
> + continue;
> +
> + if (node->stamp > target)
> + continue;
> +
> + flush_count = i915_scheduler_priority_bump(scheduler,
> + node, scheduler->priority_level_max);
> + }
> + spin_unlock_irq(&scheduler->lock);
> +
> + if (flush_count) {
> + DRM_DEBUG_DRIVER("<%s> Bumped %d entries\n", ring->name, flush_count);
> + flush_count = i915_scheduler_submit_max_priority(ring, is_locked);
> + }
> +
> + return flush_count;
> +}
> +
> +/**
> + * i915_scheduler_flush - force all requests through the scheduler.
> + * @ring: Ring to be flushed
> + * @is_locked: Is the driver mutex lock held?
> + * For various reasons it is sometimes necessary to the scheduler out, e.g.
> + * due to ring reset.
> + * Returns zero on success or -EAGAIN if the scheduler is busy (e.g. waiting
> + * for a pre-emption event to complete) but the mutex lock is held which
> + * would prevent the scheduler's asynchronous processing from completing.
> + */
> +int i915_scheduler_flush(struct intel_engine_cs *ring, bool is_locked)
> +{
> + struct i915_scheduler_queue_entry *node;
> + struct drm_i915_private *dev_priv;
> + struct i915_scheduler *scheduler;
> + bool found;
> + int ret;
> + uint32_t count = 0;
> +
> + if (!ring)
> + return -EINVAL;
> +
> + dev_priv = ring->dev->dev_private;
> + scheduler = dev_priv->scheduler;
> +
> + if (!scheduler)
> + return 0;
> +
> + WARN_ON(is_locked && (scheduler->flags[ring->id] & i915_sf_submitting));
> +
> + do {
> + found = false;
> + spin_lock_irq(&scheduler->lock);
> + list_for_each_entry(node, &scheduler->node_queue[ring->id], link) {
> + if (!I915_SQS_IS_QUEUED(node))
> + continue;
> +
> + found = true;
> + break;
> + }
> + spin_unlock_irq(&scheduler->lock);
> +
> + if (found) {
> + if (is_locked)
> + ret = i915_scheduler_submit(ring);
> + else
> + ret = i915_scheduler_submit_unlocked(ring);
> + if (ret < 0)
> + return ret;
> +
> + count += ret;
> + }
> + } while (found);
> +
> + return count;
> +}
> +
> /**
> * i915_scheduler_is_request_tracked - return info to say what the scheduler's
> * connection to this request is (if any).
> diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
> index a88adce..839b048 100644
> --- a/drivers/gpu/drm/i915/i915_scheduler.h
> +++ b/drivers/gpu/drm/i915/i915_scheduler.h
> @@ -94,6 +94,9 @@ int i915_scheduler_queue_execbuffer(struct i915_scheduler_queue_entry *qe);
> bool i915_scheduler_notify_request(struct drm_i915_gem_request *req);
> void i915_scheduler_wakeup(struct drm_device *dev);
> void i915_scheduler_work_handler(struct work_struct *work);
> +int i915_scheduler_flush(struct intel_engine_cs *ring, bool is_locked);
> +int i915_scheduler_flush_stamp(struct intel_engine_cs *ring,
> + unsigned long stamp, bool is_locked);
> bool i915_scheduler_is_request_tracked(struct drm_i915_gem_request *req,
> bool *completed, bool *busy);
>
--
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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