[Intel-gfx] [PATCH] drm/i915: During shrink_all we only need to idle the GPU

[Chris Wilson]

We can forgo an evict-everything here as the shrinker operation itself
will unbind any vma as required. If we explicitly idle the GPU through a
switch to the default context, we not only create a request in an
illegal context (e.g. whilst shrinking during execbuf with a request
already allocated), but switching to the default context will not free
up the memory backing the active contexts - unless in the unlikely
situation that context had already been closed (and just kept arrive by
being the current context). The saving is near zero and the danger real.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_shrinker.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index c41ddf92e404..2d8c79b8c378 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -158,9 +158,16 @@ i915_gem_shrink(struct drm_i915_private *dev_priv,
  */
 unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
 {
-	i915_gem_evict_everything(dev_priv->dev);
-	return i915_gem_shrink(dev_priv, LONG_MAX,
-			       I915_SHRINK_BOUND | I915_SHRINK_UNBOUND);
+	unsigned long count;
+
+	count = i915_gem_shrink(dev_priv, LONG_MAX,
+				I915_SHRINK_BOUND | I915_SHRINK_UNBOUND);
+
+	/* Use a double call to retire to flush any staged frees  */
+	i915_gem_retire_requests(dev_priv->dev);
+	i915_gem_retire_requests(dev_priv->dev);
+
+	return count;
 }
 
 static bool i915_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
-- 
2.1.4