From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
This reduces the cost of the software engine busyness tracking
to a single no-op instruction when there are no listeners.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_engine_cs.c | 17 +++++++++++
drivers/gpu/drm/i915/intel_ringbuffer.h | 54 ++++++++++++++++++---------------
2 files changed, 47 insertions(+), 24 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index e709f4edef90..fb61df3f770c 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -21,6 +21,7 @@
* IN THE SOFTWARE.
*
*/
+#include <linux/static_key.h>
#include "i915_drv.h"
#include "intel_ringbuffer.h"
@@ -1347,6 +1348,10 @@ void intel_engines_mark_idle(struct drm_i915_private *i915)
}
}
+DEFINE_STATIC_KEY_FALSE(i915_engine_stats_key);
+static DEFINE_MUTEX(i915_engine_stats_mutex);
+static int i915_engine_stats_ref;
+
int intel_enable_engine_stats(struct intel_engine_cs *engine)
{
unsigned long flags;
@@ -1354,6 +1359,8 @@ int intel_enable_engine_stats(struct intel_engine_cs *engine)
if (!i915.enable_execlists)
return -ENODEV;
+ mutex_lock(&i915_engine_stats_mutex);
+
spin_lock_irqsave(&engine->stats.lock, flags);
if (engine->stats.enabled++ == 0) {
engine->stats.ref = 0;
@@ -1363,10 +1370,16 @@ int intel_enable_engine_stats(struct intel_engine_cs *engine)
}
spin_unlock_irqrestore(&engine->stats.lock, flags);
+ if (i915_engine_stats_ref++ == 0)
+ static_branch_enable(&i915_engine_stats_key);
+
+ mutex_unlock(&i915_engine_stats_mutex);
+
return 0;
busy:
spin_unlock_irqrestore(&engine->stats.lock, flags);
+ mutex_unlock(&i915_engine_stats_mutex);
return -EBUSY;
}
@@ -1378,10 +1391,14 @@ void intel_disable_engine_stats(struct intel_engine_cs *engine)
if (!i915.enable_execlists)
return;
+ mutex_lock(&i915_engine_stats_mutex);
spin_lock_irqsave(&engine->stats.lock, flags);
WARN_ON_ONCE(engine->stats.enabled == 0);
engine->stats.enabled--;
spin_unlock_irqrestore(&engine->stats.lock, flags);
+ if (--i915_engine_stats_ref == 0)
+ static_branch_disable(&i915_engine_stats_key);
+ mutex_unlock(&i915_engine_stats_mutex);
}
int intel_enable_engines_stats(struct drm_i915_private *dev_priv)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index fd5d838ca7b5..74add0a18e7d 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -754,48 +754,54 @@ void intel_engines_reset_default_submission(struct drm_i915_private *i915);
struct intel_engine_cs *
intel_engine_lookup_user(struct drm_i915_private *i915, u8 class, u8 instance);
+DECLARE_STATIC_KEY_FALSE(i915_engine_stats_key);
+
static inline void intel_engine_context_in(struct intel_engine_cs *engine)
{
unsigned long flags;
- if (READ_ONCE(engine->stats.enabled) == 0)
- return;
+ if (static_branch_unlikely(&i915_engine_stats_key)) {
+ if (READ_ONCE(engine->stats.enabled) == 0)
+ return;
- spin_lock_irqsave(&engine->stats.lock, flags);
+ spin_lock_irqsave(&engine->stats.lock, flags);
- if (engine->stats.enabled > 0) {
- if (engine->stats.ref++ == 0)
- engine->stats.start = ktime_get();
- GEM_BUG_ON(engine->stats.ref == 0);
- }
+ if (engine->stats.enabled > 0) {
+ if (engine->stats.ref++ == 0)
+ engine->stats.start = ktime_get();
+ GEM_BUG_ON(engine->stats.ref == 0);
+ }
- spin_unlock_irqrestore(&engine->stats.lock, flags);
+ spin_unlock_irqrestore(&engine->stats.lock, flags);
+ }
}
static inline void intel_engine_context_out(struct intel_engine_cs *engine)
{
unsigned long flags;
- if (READ_ONCE(engine->stats.enabled) == 0)
- return;
+ if (static_branch_unlikely(&i915_engine_stats_key)) {
+ if (READ_ONCE(engine->stats.enabled) == 0)
+ return;
- spin_lock_irqsave(&engine->stats.lock, flags);
+ spin_lock_irqsave(&engine->stats.lock, flags);
- if (engine->stats.enabled > 0) {
- /*
- * After turning on engine stats, context out might be the
- * first event which then needs to be ignored (ref == 0).
- */
- if (engine->stats.ref && --engine->stats.ref == 0) {
- ktime_t last = ktime_sub(ktime_get(),
- engine->stats.start);
+ if (engine->stats.enabled > 0) {
+ /*
+ * After turning on engine stats, context out might be
+ * the first event which then needs to be ignored.
+ */
+ if (engine->stats.ref && --engine->stats.ref == 0) {
+ ktime_t last = ktime_sub(ktime_get(),
+ engine->stats.start);
- engine->stats.total = ktime_add(engine->stats.total,
- last);
+ engine->stats.total =
+ ktime_add(engine->stats.total, last);
+ }
}
- }
- spin_unlock_irqrestore(&engine->stats.lock, flags);
+ spin_unlock_irqrestore(&engine->stats.lock, flags);
+ }
}
int intel_enable_engine_stats(struct intel_engine_cs *engine);
--
2.9.4
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