From 349bdb68bd48f4e1861058ac2dbaa0aafd4ca38d Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 17 May 2017 13:10:05 +0100 Subject: [PATCH] drm/i915/execlists: Reduce lock contention between schedule/submit_request If we do not require to perform priority bumping, and we haven't yet submitted the request, we can update its priority in situ and skip acquiring the engine locks -- thus avoiding any contention between us and submit/execute. v2: Remove the stack element from the list if we can do the early assignment. Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/20170517121007.27224-10-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/intel_lrc.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 8529746dd7cc..014b30ace8a0 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -779,6 +779,19 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio) list_safe_reset_next(dep, p, dfs_link); } + /* If we didn't need to bump any existing priorities, and we haven't + * yet submitted this request (i.e. there is no potential race with + * execlists_submit_request()), we can set our own priority and skip + * acquiring the engine locks. + */ + if (request->priotree.priority == INT_MIN) { + GEM_BUG_ON(!list_empty(&request->priotree.link)); + request->priotree.priority = prio; + if (stack.dfs_link.next == stack.dfs_link.prev) + return; + __list_del_entry(&stack.dfs_link); + } + engine = request->engine; spin_lock_irq(&engine->timeline->lock); -- 2.45.2