[PATCH 06/10] drm/i915: Maintain LRU order of inactive objects upon access by CPU (v2)

[Chris Wilson]

BugLink: http://bugs.launchpad.net/bugs/599017

In order to reduce the penalty of fallbacks under memory pressure and to
avoid a potential immediate ping-pong of evicting a mmaped buffer, we
move the object to the tail of the inactive list when a page is freshly
faulted or the object is moved into the CPU domain.

We choose not to protect the CPU objects from casual eviction,
preferring to keep the GPU active for as long as possible.

v2: Daniel Vetter found a bug where I forgot that pinned objects are
kept off the inactive list.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
(backported from commit 7d1c4804ae98cdee572d7d10d8a5deaa2e686285 upstream)

Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem.c |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2e4ff69..b3c7bd1 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -55,6 +55,14 @@ static int i915_gem_phys_pwrite(struct drm_device *dev, struct drm_gem_object *o
 static LIST_HEAD(shrink_list);
 static DEFINE_SPINLOCK(shrink_list_lock);

+static inline bool
+i915_gem_object_is_inactive(struct drm_i915_gem_object *obj_priv)
+{
+	return obj_priv->gtt_space &&
+		!obj_priv->active &&
+		obj_priv->pin_count == 0;
+}
+
 int i915_gem_do_init(struct drm_device *dev, unsigned long start,
 		     unsigned long end)
 {
@@ -1068,6 +1076,11 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
 		ret = i915_gem_object_set_to_cpu_domain(obj, write_domain != 0);
 	}

+
+	/* Maintain LRU order of "inactive" objects */
+	if (ret == 0 && i915_gem_object_is_inactive(obj_priv))
+		list_move_tail(&obj_priv->list, &dev_priv->mm.inactive_list);
+
 	drm_gem_object_unreference(obj);
 	mutex_unlock(&dev->struct_mutex);
 	return ret;
@@ -1203,6 +1216,9 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 			goto unlock;
 	}

+	if (i915_gem_object_is_inactive(obj_priv))
+		list_move_tail(&obj_priv->list, &dev_priv->mm.inactive_list);
+
 	pfn = ((dev->agp->base + obj_priv->gtt_offset) >> PAGE_SHIFT) +
 		page_offset;

--
1.7.4.1

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