This provides a nice boost to mesa in swap bound scenarios (as mesa
throttles itself to the previous frame and given the scenario that will
complete shortly). It will also provide a good boost to systems running
with semaphores disabled and so frequently waiting on the GPU as it
switches rings.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 43 +++++++++++++++++++++++++++++++++++------
1 file changed, 37 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index de15bd319bd0..2aaa3cab2be4 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1191,6 +1191,28 @@ static bool missed_irq(struct drm_i915_private *dev_priv,
return test_bit(ring->id, &dev_priv->gpu_error.missed_irq_rings);
}
+static int __i915_spin_request(struct drm_i915_gem_request *req)
+{
+ struct intel_engine_cs *ring = i915_gem_request_get_ring(req);
+ struct drm_i915_private *dev_priv = to_i915(ring->dev);
+ int ret = -EBUSY;
+
+ intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
+ while (!need_resched()) {
+ if (i915_gem_request_completed(req, true)) {
+ ret = 0;
+ goto out;
+ }
+
+ cpu_relax_lowlatency();
+ }
+ if (i915_gem_request_completed(req, false))
+ ret = 0;
+out:
+ intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
+ return ret;
+}
+
/**
* __i915_wait_request - wait until execution of request has finished
* @req: duh!
@@ -1235,12 +1257,20 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
if (ring->id == RCS && INTEL_INFO(dev)->gen >= 6)
gen6_rps_boost(dev_priv, file_priv);
- if (!irq_test_in_progress && WARN_ON(!ring->irq_get(ring)))
- return -ENODEV;
-
/* Record current time in case interrupted by signal, or wedged */
trace_i915_gem_request_wait_begin(req);
before = ktime_get_raw_ns();
+
+ /* Optimistic spin before touching IRQs */
+ ret = __i915_spin_request(req);
+ if (ret == 0)
+ goto out;
+
+ if (!irq_test_in_progress && WARN_ON(!ring->irq_get(ring))) {
+ ret = -ENODEV;
+ goto out;
+ }
+
for (;;) {
struct timer_list timer;
@@ -1289,14 +1319,15 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
destroy_timer_on_stack(&timer);
}
}
- now = ktime_get_raw_ns();
- trace_i915_gem_request_wait_end(req);
-
if (!irq_test_in_progress)
ring->irq_put(ring);
finish_wait(&ring->irq_queue, &wait);
+out:
+ now = ktime_get_raw_ns();
+ trace_i915_gem_request_wait_end(req);
+
if (timeout) {
s64 tres = *timeout - (now - before);
--
2.1.4
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