Commit 07bfe6bf authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/execlists: Convert recursive defer_request() into iterative 



As this engine owns the lock around rq->sched.link (for those waiters
submitted to this engine), we can use that link as an element in a local
list. We can thus replace the recursive algorithm with an iterative walk
over the ordered list of waiters.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190625130128.11009-1-chris@chris-wilson.co.uk
parent 9a6a6440

drivers/gpu/drm/i915/gt/intel_lrc.c

+27 −25
Original line number Diff line number Diff line
@@ -833,10 +833,9 @@ last_active(const struct intel_engine_execlists *execlists) 
	return *last;

}



static void

defer_request(struct i915_request * const rq, struct list_head * const pl)

static void defer_request(struct i915_request *rq, struct list_head * const pl)

{

	struct i915_dependency *p;

	LIST_HEAD(list);



	/*

	 * We want to move the interrupted request to the back of
@@ -845,6 +844,10 @@ defer_request(struct i915_request * const rq, struct list_head * const pl) 
	 * flight and were waiting for the interrupted request to

	 * be run after it again.

	 */

	do {

		struct i915_dependency *p;



		GEM_BUG_ON(i915_request_is_active(rq));

		list_move_tail(&rq->sched.link, pl);



		list_for_each_entry(p, &rq->sched.waiters_list, wait_link) {
@@ -855,24 +858,23 @@ defer_request(struct i915_request * const rq, struct list_head * const pl) 
			if (w->engine != rq->engine)

				continue;



		/* No waiter should start before the active request completed */

		GEM_BUG_ON(i915_request_started(w));



		GEM_BUG_ON(rq_prio(w) > rq_prio(rq));

		if (rq_prio(w) < rq_prio(rq))

			continue;

			/* No waiter should start before its signaler */

			GEM_BUG_ON(i915_request_started(w) &&

				   !i915_request_completed(rq));



			GEM_BUG_ON(i915_request_is_active(w));

			if (list_empty(&w->sched.link))

				continue; /* Not yet submitted; unready */



		/*

		 * This should be very shallow as it is limited by the

		 * number of requests that can fit in a ring (<64) and

		 * the number of contexts that can be in flight on this

		 * engine.

		 */

		defer_request(w, pl);

			if (rq_prio(w) < rq_prio(rq))

				continue;



			GEM_BUG_ON(rq_prio(w) > rq_prio(rq));

			list_move_tail(&w->sched.link, &list);

		}



		rq = list_first_entry_or_null(&list, typeof(*rq), sched.link);

	} while (rq);

}



static void defer_active(struct intel_engine_cs *engine)

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