[Intel-gfx] [PATCH 3/8] drm/i915: evict VM instead of everything

[Ben Widawsky]

When reserving objects during execbuf, it is possible to come across an
object which will not fit given the current fragmentation of the address
space. We do not have any defragment in drm_mm, so the strategy is to
instead evict everything, and reallocate objects.

With the upcoming addition of multiple VMs, there is no point to evict
everything since doing so is overkill for the specific case mentioned
above.

Recommended-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_drv.h            |  1 +
 drivers/gpu/drm/i915/i915_gem_evict.c      | 17 ++++++++++++++++-
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |  8 +++++++-
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 81ba5bb..7caf71d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2106,6 +2106,7 @@ int __must_check i915_gem_evict_something(struct drm_device *dev,
 					  unsigned cache_level,
 					  bool mappable,
 					  bool nonblock);
+int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);
 int i915_gem_evict_everything(struct drm_device *dev);
 
 /* i915_gem_stolen.c */
diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index e9033f0..a3e279d 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -155,7 +155,22 @@ found:
 	return ret;
 }
 
-static int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle)
+/**
+ * i915_gem_evict_vm - Try to free up VM space
+ *
+ * @vm: Address space to evict from
+ * @do_idle: Boolean directing whether to idle first.
+ *
+ * VM eviction is about freeing up virtual address space. If one wants fine
+ * grained eviction, they should see evict something for more details. In terms
+ * of freeing up actual system memory, this function may not accomplish the
+ * desired result. An object may be shared in multiple address space, and this
+ * function will not assert those objects be freed.
+ *
+ * Using do_idle will result in a more complete eviction because it retires, and
+ * inactivates current BOs.
+ */
+int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle)
 {
 	struct i915_vma *vma, *next;
 	int ret;
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index c8a01c1..ee93357 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -549,10 +549,16 @@ i915_gem_execbuffer_reserve(struct intel_ring_buffer *ring,
 {
 	struct drm_i915_gem_object *obj;
 	struct i915_vma *vma;
+	struct i915_address_space *vm;
 	struct list_head ordered_vmas;
 	bool has_fenced_gpu_access = INTEL_INFO(ring->dev)->gen < 4;
 	int retry;
 
+	if (list_empty(vmas))
+		return 0;
+
+	vm = list_first_entry(vmas, struct i915_vma, exec_list)->vm;
+
 	INIT_LIST_HEAD(&ordered_vmas);
 	while (!list_empty(vmas)) {
 		struct drm_i915_gem_exec_object2 *entry;
@@ -641,7 +647,7 @@ err:		/* Decrement pin count for bound objects */
 		if (ret != -ENOSPC || retry++)
 			return ret;
 
-		ret = i915_gem_evict_everything(ring->dev);
+		ret = i915_gem_evict_vm(vm, true);
 		if (ret)
 			return ret;
 	} while (1);
-- 
1.8.4