From c22b355ff7fd60378c55d1401530287fea4e3a96 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 7 Feb 2018 08:43:49 +0000 Subject: [PATCH] drm/i915: Trim the retired request queue after submitting If we submit a request and see that the previous request on this timeline was already signaled, we first do not need to add the dependency tracker for that completed request and secondly we know that we there is then a large backlog in retiring requests affecting this timeline. Given that we just submitted more work to the HW, now would be a good time to catch up on those retirements. v2: Try to sum up the compromises involved in flushing the retirement queue after submission. Signed-off-by: Chris Wilson Cc: Joonas Lahtinen Cc: Tvrtko Ursulin Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20180207084350.3929-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem_request.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c index e5f8762..a8eb22a 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.c +++ b/drivers/gpu/drm/i915/i915_gem_request.c @@ -1077,6 +1077,26 @@ void __i915_add_request(struct drm_i915_gem_request *request, bool flush_caches) local_bh_disable(); i915_sw_fence_commit(&request->submit); local_bh_enable(); /* Kick the execlists tasklet if just scheduled */ + + /* + * In typical scenarios, we do not expect the previous request on + * the timeline to be still tracked by timeline->last_request if it + * has been completed. If the completed request is still here, that + * implies that request retirement is a long way behind submission, + * suggesting that we haven't been retiring frequently enough from + * the combination of retire-before-alloc, waiters and the background + * retirement worker. So if the last request on this timeline was + * already completed, do a catch up pass, flushing the retirement queue + * up to this client. Since we have now moved the heaviest operations + * during retirement onto secondary workers, such as freeing objects + * or contexts, retiring a bunch of requests is mostly list management + * (and cache misses), and so we should not be overly penalizing this + * client by performing excess work, though we may still performing + * work on behalf of others -- but instead we should benefit from + * improved resource management. (Well, that's the theory at least.) + */ + if (prev && i915_gem_request_completed(prev)) + i915_gem_request_retire_upto(prev); } static unsigned long local_clock_us(unsigned int *cpu) -- 2.7.4