[PATCH v5 19/35] drm/i915: Added scheduler flush calls to ring throttle and idle functions

From: John.C.Harrison@Intel.com
To: Intel-GFX@Lists.FreeDesktop.Org
Subject: [PATCH v5 19/35] drm/i915: Added scheduler flush calls to ring throttle and idle functions
Date: Thu, 18 Feb 2016 14:27:07 +0000	[thread overview]
Message-ID: <1455805644-6450-20-git-send-email-John.C.Harrison@Intel.com> (raw)
In-Reply-To: <1455805644-6450-1-git-send-email-John.C.Harrison@Intel.com>

From: John Harrison <John.C.Harrison@Intel.com>

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@Intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 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;
+}
+
 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);
+		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;
+	}
+
+	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);
 
-- 
1.9.1

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