[PATCH 29/40] drm/i915: Added scheduler queue throttling by DRM file handle

[John.C.Harrison@Intel.com]

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

The scheduler decouples the submission of batch buffers to the driver
from their subsequent submission to the hardware. This means that an
application which is continuously submitting buffers as fast as it can
could potentialy flood the driver. To prevent this, the driver now
tracks how many buffers are in progress (queued in software or
executing in hardware) and limits this to a given (tunable) number. If
this number is exceeded then the queue to the driver will return
EAGAIN and thus prevent the scheduler's queue becoming arbitrarily
large.

v3: Added a missing decrement of the file queue counter.

Change-Id: I83258240aec7c810db08c006a3062d46aa91363f
For: VIZ-1587
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h            |  2 ++
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |  8 +++++++
 drivers/gpu/drm/i915/i915_scheduler.c      | 35 ++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_scheduler.h      |  2 ++
 4 files changed, 47 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 4187e75..4ecb6e4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -342,6 +342,8 @@ struct drm_i915_file_private {
 	} rps;
 
 	struct intel_engine_cs *bsd_ring;
+
+	u32 scheduler_queue_length;
 };
 
 enum intel_dpll_id {
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index b358b21..8ba426f 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1862,6 +1862,10 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
+	/* Throttle batch requests per device file */
+	if (i915_scheduler_file_queue_is_full(file))
+		return -EAGAIN;
+
 	/* Copy in the exec list from userland */
 	exec_list = drm_malloc_ab(sizeof(*exec_list), args->buffer_count);
 	exec2_list = drm_malloc_ab(sizeof(*exec2_list), args->buffer_count);
@@ -1945,6 +1949,10 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
+	/* Throttle batch requests per device file */
+	if (i915_scheduler_file_queue_is_full(file))
+		return -EAGAIN;
+
 	exec2_list = kmalloc(sizeof(*exec2_list)*args->buffer_count,
 			     GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
 	if (exec2_list == NULL)
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 4736f0f..e6e1bd967 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -40,6 +40,8 @@ static void        i915_scheduler_priority_bump_clear(struct i915_scheduler *sch
 static int         i915_scheduler_priority_bump(struct i915_scheduler *scheduler,
 						struct i915_scheduler_queue_entry *target,
 						uint32_t bump);
+static void        i915_scheduler_file_queue_inc(struct drm_file *file);
+static void        i915_scheduler_file_queue_dec(struct drm_file *file);
 
 bool i915_scheduler_is_enabled(struct drm_device *dev)
 {
@@ -74,6 +76,7 @@ int i915_scheduler_init(struct drm_device *dev)
 	scheduler->priority_level_max     = 1023;
 	scheduler->priority_level_preempt = 900;
 	scheduler->min_flying             = 2;
+	scheduler->file_queue_max         = 64;
 
 	dev_priv->scheduler = scheduler;
 
@@ -267,6 +270,8 @@ int i915_scheduler_queue_execbuffer(struct i915_scheduler_queue_entry *qe)
 
 	list_add_tail(&node->link, &scheduler->node_queue[ring->id]);
 
+	i915_scheduler_file_queue_inc(node->params.file);
+
 	if (i915.scheduler_override & i915_so_submit_on_queue)
 		not_flying = true;
 	else
@@ -551,6 +556,12 @@ static int i915_scheduler_remove(struct intel_engine_cs *ring)
 		/* Strip the dependency info while the mutex is still locked */
 		i915_scheduler_remove_dependent(scheduler, node);
 
+		/* Likewise clean up the file descriptor before it might disappear. */
+		if (node->params.file) {
+			i915_scheduler_file_queue_dec(node->params.file);
+			node->params.file = NULL;
+		}
+
 		continue;
 	}
 
@@ -1194,6 +1205,7 @@ int i915_scheduler_closefile(struct drm_device *dev, struct drm_file *file)
 						 node->status,
 						 ring->name);
 
+			i915_scheduler_file_queue_dec(node->params.file);
 			node->params.file = NULL;
 		}
 	}
@@ -1202,3 +1214,26 @@ int i915_scheduler_closefile(struct drm_device *dev, struct drm_file *file)
 
 	return 0;
 }
+
+bool i915_scheduler_file_queue_is_full(struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct drm_i915_private      *dev_priv  = file_priv->dev_priv;
+	struct i915_scheduler        *scheduler = dev_priv->scheduler;
+
+	return file_priv->scheduler_queue_length >= scheduler->file_queue_max;
+}
+
+static void i915_scheduler_file_queue_inc(struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+
+	file_priv->scheduler_queue_length++;
+}
+
+static void i915_scheduler_file_queue_dec(struct drm_file *file)
+{
+	struct drm_i915_file_private *file_priv = file->driver_priv;
+
+	file_priv->scheduler_queue_length--;
+}
diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index b10f30c..5de0506 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -82,6 +82,7 @@ struct i915_scheduler {
 	int32_t             priority_level_max;
 	int32_t             priority_level_preempt;
 	uint32_t            min_flying;
+	uint32_t            file_queue_max;
 };
 
 /* Flag bits for i915_scheduler::flags */
@@ -110,5 +111,6 @@ 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);
+bool        i915_scheduler_file_queue_is_full(struct drm_file *file);
 
 #endif  /* _I915_SCHEDULER_H_ */
-- 
1.9.1

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