From 7ec2c73b1dbe1cd83c52e4a386b2070331c5414c Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 1 Jul 2016 17:23:22 +0100 Subject: [PATCH] drm/i915: Check the CPU cached value in HWS of seqno after waking the waiter If we have multiple waiters, we may find that many complete on the same wake up. If we first inspect the seqno from the CPU cache, we may reduce the number of heavyweight coherent seqno reads we require. Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/1467390209-3576-13-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_drv.h | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 5a1e8e0..ee04bd4 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -3988,6 +3988,12 @@ static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req) { struct intel_engine_cs *engine = req->engine; + /* Before we do the heavier coherent read of the seqno, + * check the value (hopefully) in the CPU cacheline. + */ + if (i915_gem_request_completed(req)) + return true; + /* Ensure our read of the seqno is coherent so that we * do not "miss an interrupt" (i.e. if this is the last * request and the seqno write from the GPU is not visible @@ -3999,11 +4005,11 @@ static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req) * but it is easier and safer to do it every time the waiter * is woken. */ - if (engine->irq_seqno_barrier) + if (engine->irq_seqno_barrier) { engine->irq_seqno_barrier(engine); - - if (i915_gem_request_completed(req)) - return true; + if (i915_gem_request_completed(req)) + return true; + } /* We need to check whether any gpu reset happened in between * the request being submitted and now. If a reset has occurred, -- 2.7.4