From: Chris Wilson Date: Tue, 9 Apr 2019 15:29:22 +0000 (+0100) Subject: drm/i915: Bump ready tasks ahead of busywaits X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=b7404c7ecb38b66f103cec694e23a8e99252829e;p=openwrt%2Fstaging%2Fblogic.git drm/i915: Bump ready tasks ahead of busywaits Consider two tasks that are running in parallel on a pair of engines (vcs0, vcs1), but then must complete on a shared engine (rcs0). To maximise throughput, we want to run the first ready task on rcs0 (i.e. the first task that completes on either of vcs0 or vcs1). When using semaphores, however, we will instead queue onto rcs in submission order. To resolve this incorrect ordering, we want to re-evaluate the priority queue when each of the request is ready. Normally this happens because we only insert into the priority queue requests that are ready, but with semaphores we are inserting ahead of their readiness and to compensate we penalize those tasks with reduced priority (so that tasks that do not need to busywait should naturally be run first). However, given a series of tasks that each use semaphores, the queue degrades into submission fifo rather than readiness fifo, and so to counter this we give a small boost to semaphore users as their dependent tasks are completed (and so we no longer require any busywait prior to running the user task as they are then ready themselves). v2: Fixup irqsave for schedule_lock (Tvrtko) Testcase: igt/gem_exec_schedule/semaphore-codependency Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Dmitry Rogozhkin Cc: Dmitry Ermilov Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20190409152922.23894-1-chris@chris-wilson.co.uk --- diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c index 96a9e8bcd805..a7d87cfaabcb 100644 --- a/drivers/gpu/drm/i915/i915_request.c +++ b/drivers/gpu/drm/i915/i915_request.c @@ -552,6 +552,36 @@ submit_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state) return NOTIFY_DONE; } +static int __i915_sw_fence_call +semaphore_notify(struct i915_sw_fence *fence, enum i915_sw_fence_notify state) +{ + struct i915_request *request = + container_of(fence, typeof(*request), semaphore); + + switch (state) { + case FENCE_COMPLETE: + /* + * We only check a small portion of our dependencies + * and so cannot guarantee that there remains no + * semaphore chain across all. Instead of opting + * for the full NOSEMAPHORE boost, we go for the + * smaller (but still preempting) boost of + * NEWCLIENT. This will be enough to boost over + * a busywaiting request (as that cannot be + * NEWCLIENT) without accidentally boosting + * a busywait over real work elsewhere. + */ + i915_schedule_bump_priority(request, I915_PRIORITY_NEWCLIENT); + break; + + case FENCE_FREE: + i915_request_put(request); + break; + } + + return NOTIFY_DONE; +} + static void ring_retire_requests(struct intel_ring *ring) { struct i915_request *rq, *rn; @@ -702,6 +732,7 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx) /* We bump the ref for the fence chain */ i915_sw_fence_init(&i915_request_get(rq)->submit, submit_notify); + i915_sw_fence_init(&i915_request_get(rq)->semaphore, semaphore_notify); i915_sched_node_init(&rq->sched); @@ -784,6 +815,12 @@ emit_semaphore_wait(struct i915_request *to, &from->fence, 0, I915_FENCE_GFP); + err = i915_sw_fence_await_dma_fence(&to->semaphore, + &from->fence, 0, + I915_FENCE_GFP); + if (err < 0) + return err; + /* We need to pin the signaler's HWSP until we are finished reading. */ err = i915_timeline_read_hwsp(from, to, &hwsp_offset); if (err) @@ -1114,6 +1151,7 @@ void i915_request_add(struct i915_request *request) * run at the earliest possible convenience. */ local_bh_disable(); + i915_sw_fence_commit(&request->semaphore); rcu_read_lock(); /* RCU serialisation for set-wedged protection */ if (engine->schedule) { struct i915_sched_attr attr = request->gem_context->sched; @@ -1320,7 +1358,9 @@ long i915_request_wait(struct i915_request *rq, if (flags & I915_WAIT_PRIORITY) { if (!i915_request_started(rq) && INTEL_GEN(rq->i915) >= 6) gen6_rps_boost(rq); + local_bh_disable(); /* suspend tasklets for reprioritisation */ i915_schedule_bump_priority(rq, I915_PRIORITY_WAIT); + local_bh_enable(); /* kick tasklets en masse */ } wait.tsk = current; diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h index 875be6f71412..a982664618c2 100644 --- a/drivers/gpu/drm/i915/i915_request.h +++ b/drivers/gpu/drm/i915/i915_request.h @@ -143,6 +143,7 @@ struct i915_request { struct i915_sw_dma_fence_cb dmaq; }; struct list_head execute_cb; + struct i915_sw_fence semaphore; /* * A list of everyone we wait upon, and everyone who waits upon us. diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c index 77dbf7d74e12..39bc4f54e272 100644 --- a/drivers/gpu/drm/i915/i915_scheduler.c +++ b/drivers/gpu/drm/i915/i915_scheduler.c @@ -64,7 +64,7 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, { bool ret = false; - spin_lock(&schedule_lock); + spin_lock_irq(&schedule_lock); if (!node_signaled(signal)) { INIT_LIST_HEAD(&dep->dfs_link); @@ -81,7 +81,7 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node, ret = true; } - spin_unlock(&schedule_lock); + spin_unlock_irq(&schedule_lock); return ret; } @@ -108,7 +108,7 @@ void i915_sched_node_fini(struct i915_sched_node *node) GEM_BUG_ON(!list_empty(&node->link)); - spin_lock(&schedule_lock); + spin_lock_irq(&schedule_lock); /* * Everyone we depended upon (the fences we wait to be signaled) @@ -135,7 +135,7 @@ void i915_sched_node_fini(struct i915_sched_node *node) i915_dependency_free(dep); } - spin_unlock(&schedule_lock); + spin_unlock_irq(&schedule_lock); } static inline struct i915_priolist *to_priolist(struct rb_node *rb) @@ -356,7 +356,7 @@ static void __i915_schedule(struct i915_request *rq, memset(&cache, 0, sizeof(cache)); engine = rq->engine; - spin_lock_irq(&engine->timeline.lock); + spin_lock(&engine->timeline.lock); /* Fifo and depth-first replacement ensure our deps execute before us */ list_for_each_entry_safe_reverse(dep, p, &dfs, dfs_link) { @@ -407,32 +407,33 @@ static void __i915_schedule(struct i915_request *rq, tasklet_hi_schedule(&engine->execlists.tasklet); } - spin_unlock_irq(&engine->timeline.lock); + spin_unlock(&engine->timeline.lock); } void i915_schedule(struct i915_request *rq, const struct i915_sched_attr *attr) { - spin_lock(&schedule_lock); + spin_lock_irq(&schedule_lock); __i915_schedule(rq, attr); - spin_unlock(&schedule_lock); + spin_unlock_irq(&schedule_lock); } void i915_schedule_bump_priority(struct i915_request *rq, unsigned int bump) { struct i915_sched_attr attr; + unsigned long flags; GEM_BUG_ON(bump & ~I915_PRIORITY_MASK); if (READ_ONCE(rq->sched.attr.priority) == I915_PRIORITY_INVALID) return; - spin_lock_bh(&schedule_lock); + spin_lock_irqsave(&schedule_lock, flags); attr = rq->sched.attr; attr.priority |= bump; __i915_schedule(rq, &attr); - spin_unlock_bh(&schedule_lock); + spin_unlock_irqrestore(&schedule_lock, flags); } void __i915_priolist_free(struct i915_priolist *p)