@@ -334,6 +334,7 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id)
/* Nothing to do here, execute in order of dependencies */
engine->schedule = NULL;
+ ewma__engine_latency_init(&engine->latency);
seqlock_init(&engine->stats.lock);
ATOMIC_INIT_NOTIFIER_HEAD(&engine->context_status_notifier);
@@ -1481,6 +1482,8 @@ void intel_engine_dump(struct intel_engine_cs *engine,
drm_printf(m, "\tAwake? %d\n", atomic_read(&engine->wakeref.count));
drm_printf(m, "\tBarriers?: %s\n",
yesno(!llist_empty(&engine->barrier_tasks)));
+ drm_printf(m, "\tLatency: %luus\n",
+ ewma__engine_latency_read(&engine->latency));
rcu_read_lock();
rq = READ_ONCE(engine->heartbeat.systole);
@@ -73,6 +73,15 @@ static inline void __timeline_mark_unlock(struct intel_context *ce,
#endif /* !IS_ENABLED(CONFIG_LOCKDEP) */
+static void duration(struct dma_fence *fence, struct dma_fence_cb *cb)
+{
+ struct i915_request *rq = to_request(fence);
+
+ ewma__engine_latency_add(&rq->engine->latency,
+ ktime_us_delta(rq->fence.timestamp,
+ rq->duration.emitted));
+}
+
static void
__queue_and_release_pm(struct i915_request *rq,
struct intel_timeline *tl,
@@ -163,7 +172,18 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
/* Install ourselves as a preemption barrier */
rq->sched.attr.priority = I915_PRIORITY_BARRIER;
- __i915_request_commit(rq);
+ if (likely(!__i915_request_commit(rq))) { /* engine should be idle! */
+ /*
+ * Use an interrupt for precise measurement of duration,
+ * otherwise we rely on someone else retiring all the requests
+ * which may delay the signaling (i.e. we will likely wait
+ * until the background request retirement running every
+ * second or two).
+ */
+ BUILD_BUG_ON(sizeof(rq->duration) > sizeof(rq->submitq));
+ dma_fence_add_callback(&rq->fence, &rq->duration.cb, duration);
+ rq->duration.emitted = ktime_get();
+ }
/* Expose ourselves to the world */
__queue_and_release_pm(rq, ce->timeline, engine);
@@ -7,6 +7,7 @@
#ifndef __INTEL_ENGINE_TYPES__
#define __INTEL_ENGINE_TYPES__
+#include <linux/average.h>
#include <linux/hashtable.h>
#include <linux/irq_work.h>
#include <linux/kref.h>
@@ -119,6 +120,9 @@ enum intel_engine_id {
#define INVALID_ENGINE ((enum intel_engine_id)-1)
};
+/* A simple estimator for the round-trip latency of an engine */
+DECLARE_EWMA(_engine_latency, 6, 4)
+
struct st_preempt_hang {
struct completion completion;
unsigned int count;
@@ -316,6 +320,13 @@ struct intel_engine_cs {
struct intel_timeline *timeline;
} legacy;
+ /*
+ * We track the average duration of the idle pulse on parking the
+ * engine to keep an estimate of the how the fast the engine is
+ * under ideal conditions.
+ */
+ struct ewma__engine_latency latency;
+
/* Rather than have every client wait upon all user interrupts,
* with the herd waking after every interrupt and each doing the
* heavyweight seqno dance, we delegate the task (of being the
@@ -150,6 +150,10 @@ struct i915_request {
union {
wait_queue_entry_t submitq;
struct i915_sw_dma_fence_cb dmaq;
+ struct i915_request_duration_cb {
+ struct dma_fence_cb cb;
+ ktime_t emitted;
+ } duration;
};
struct list_head execute_cb;
struct i915_sw_fence semaphore;