[PATCH 41/67] drm/i915: Expose idle delays to Kconfig

Chris Wilson chris at chris-wilson.co.uk
Thu Jan 11 12:37:16 UTC 2018


We want to expose the parameters for controlling how long it takes for
us to notice and park the GPU after a stream of requests in order to try
and tune the optimal power-efficiency vs latency of a mostly idle system.

v2: retire_work has two scheduling points, update them both

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/Kconfig.profile    | 23 +++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_gem.c         |  2 +-
 drivers/gpu/drm/i915/i915_gem.h         | 13 +++++++++++++
 drivers/gpu/drm/i915/i915_gem_request.c |  4 ++--
 4 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
index 8a230eeb98df..63cb744d920d 100644
--- a/drivers/gpu/drm/i915/Kconfig.profile
+++ b/drivers/gpu/drm/i915/Kconfig.profile
@@ -24,3 +24,26 @@ config DRM_I915_SPIN_REQUEST_CS
 	  spin prior to sleeping again.
 
 	  May be 0 to disable spinning after being woken.
+
+config DRM_I915_GEM_RETIRE_DELAY
+	int
+	default 1000 # milliseconds
+	help
+	  We maintain a background job whose purpose is to keep cleaning up
+	  after userspace, and may be the first to spot an idle system. This
+	  parameter determines the interval between execution of the worker.
+
+	  To reduce the number of timer wakeups, large delays (of greater than
+	  a second) are rounded to the next walltime second to allow coalescing
+	  of multiple system timers into a single wakeup.
+
+config DRM_I915_GEM_PARK_DELAY
+	int
+	default 100 # milliseconds
+	help
+	  Before parking the engines and the GPU after the final request is
+	  retired, we may wait for a small delay to reduce the frequecy of
+	  having to park/unpark and so the latency in executing a new request.
+
+	  May be 0 to immediately start parking the engines after the last
+	  request.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 418c7939c57d..649ab08a9466 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4720,7 +4720,7 @@ i915_gem_retire_work_handler(struct work_struct *work)
 		i915_queue_hangcheck(dev_priv);
 		queue_delayed_work(dev_priv->wq,
 				   &dev_priv->gt.retire_work,
-				   round_jiffies_up_relative(HZ));
+				   i915_gem_retire_delay());
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
index e920dab7f1b8..7e052d1011cb 100644
--- a/drivers/gpu/drm/i915/i915_gem.h
+++ b/drivers/gpu/drm/i915/i915_gem.h
@@ -26,6 +26,8 @@
 #define __I915_GEM_H__
 
 #include <linux/bug.h>
+#include <linux/jiffies.h>
+#include <linux/timer.h>
 
 #ifdef CONFIG_DRM_I915_DEBUG_GEM
 #define GEM_BUG_ON(condition) do { if (unlikely((condition))) {	\
@@ -56,4 +58,15 @@
 
 #define I915_NUM_ENGINES 5
 
+static inline unsigned long i915_gem_retire_delay(void)
+{
+	const unsigned long delay =
+		msecs_to_jiffies(CONFIG_DRM_I915_GEM_RETIRE_DELAY);
+
+	if (CONFIG_DRM_I915_GEM_RETIRE_DELAY >= 1000)
+		return round_jiffies_up_relative(delay);
+	else
+		return delay;
+}
+
 #endif /* __I915_GEM_H__ */
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 370a158ec1e0..700fee881314 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -285,7 +285,7 @@ static void mark_busy(struct drm_i915_private *i915)
 
 	queue_delayed_work(i915->wq,
 			   &i915->gt.retire_work,
-			   round_jiffies_up_relative(HZ));
+			   i915_gem_retire_delay());
 }
 
 static int reserve_engine(struct intel_engine_cs *engine)
@@ -319,7 +319,7 @@ static void unreserve_engine(struct intel_engine_cs *engine)
 		GEM_BUG_ON(!i915->gt.awake);
 		mod_delayed_work(i915->wq,
 				 &i915->gt.idle_work,
-				 msecs_to_jiffies(100));
+				 msecs_to_jiffies(CONFIG_DRM_I915_GEM_PARK_DELAY));
 	}
 
 	GEM_BUG_ON(!engine->timeline->inflight_seqnos);
-- 
2.15.1



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