[Intel-gfx] [PATCH 2/2] drm/i915: Keep the per-object list of VMAs under control

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Where objects are shared across contexts and heavy rendering
is in progress, execlist retired request queue will grow
unbound until the GPU is idle enough for the retire worker
to run and call intel_execlists_retire_requests.

With some workloads, like for example gem_close_race, that
never happens causing the shared object VMA list to grow to
epic proportions, and in turn causes retirement call sites to
spend linearly more and more time walking the obj->vma_list.

End result is the above mentioned test case taking ten minutes
to complete and using up more than a GiB of RAM just for the VMA
objects.

If we instead trigger the execlist house keeping a bit more
often, obj->vma_list will be kept in check by the virtue of
context cleanup running and zapping the inactive VMAs.

This makes the test case an order of magnitude faster and brings
memory use back to normal.

This also makes the code more self-contained since the
intel_execlists_retire_requests call-site is now in a more
appropriate place and implementation leakage is somewhat
reduced.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Testcase: igt/gem_close_race/gem_close_race
---
 drivers/gpu/drm/i915/i915_gem.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index faa9def96917..c558887b2084 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2955,6 +2955,9 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
 		i915_gem_request_assign(&ring->trace_irq_req, NULL);
 	}
 
+	if (i915.enable_execlists)
+		intel_execlists_retire_requests(ring);
+
 	WARN_ON(i915_verify_lists(ring->dev));
 }
 
@@ -2973,8 +2976,6 @@ i915_gem_retire_requests(struct drm_device *dev)
 			spin_lock_irq(&ring->execlist_lock);
 			idle &= list_empty(&ring->execlist_queue);
 			spin_unlock_irq(&ring->execlist_lock);
-
-			intel_execlists_retire_requests(ring);
 		}
 	}
 
-- 
1.9.1