drm/i915: evict VM instead of everything

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@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
[danvet: One additional s/evict_everything/evict_vm/ to update a
comment in the code.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 17 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index e9033f02f498..3a3981eb3012 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -116,7 +116,7 @@ none:
 	}
 
 	/* We expect the caller to unpin, evict all and try again, or give up.
-	 * So calling i915_gem_evict_everything() is unnecessary.
+	 * So calling i915_gem_evict_vm() is unnecessary.
 	 */
 	return -ENOSPC;
 
@@ -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;