From: Chris Wilson Date: Thu, 19 Dec 2019 12:43:53 +0000 (+0000) Subject: drm/i915/gt: Track engine round-trip times X-Git-Tag: v5.15~3115^2~24^2~1429 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=b81e4d9b594188a8babf06442e1d6f28de78c68f;p=platform%2Fkernel%2Flinux-starfive.git drm/i915/gt: Track engine round-trip times Knowing the round trip time of an engine is useful for tracking the health of the system as well as providing a metric for the baseline responsiveness of the engine. We can use the latter metric for automatically tuning our waits in selftests and when idling so we don't confuse a slower system with a dead one. Upon idling the engine, we send one last pulse to switch the context away from precious user state to the volatile kernel context. We know the engine is idle at this point, and the pulse is non-preemptible, so this provides us with a good measurement of the round trip time. It also provides us with faster engine parking for ringbuffer submission, which is a welcome bonus (e.g. softer-rc6). Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Stuart Summers Reviewed-by: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20191219105043.4169050-1-chris@chris-wilson.co.uk Link: https://patchwork.freedesktop.org/patch/msgid/20191219124353.8607-2-chris@chris-wilson.co.uk --- diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index 3d1d48b..6dd18f9 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -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); diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c index bcbda8e..8fb7b34 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c @@ -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); diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h index 17f1f14..7f227da 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h @@ -7,6 +7,7 @@ #ifndef __INTEL_ENGINE_TYPES__ #define __INTEL_ENGINE_TYPES__ +#include #include #include #include @@ -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 diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h index aa38290..c18c0bc 100644 --- a/drivers/gpu/drm/i915/i915_request.h +++ b/drivers/gpu/drm/i915/i915_request.h @@ -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;