drm/i915: Move dev_priv->mm.[un]bound_list to its own lock

Remove the struct_mutex requirement around dev_priv->mm.bound_list and
dev_priv->mm.unbound_list by giving it its own spinlock. This reduces
one more requirement for struct_mutex and in the process gives us
slightly more accurate unbound_list tracking, which should improve the
shrinker - but the drawback is that we drop the retirement before
counting so i915_gem_object_is_active() may be stale and lead us to
underestimate the number of objects that may be shrunk (see commit
bed50aea61df ("drm/i915/shrinker: Flush active on objects before
counting")).

v2: Crosslink the spinlock to the lists it protects, and btw this
changes s/obj->global_link/obj->mm.link/
v3: Fix decoupling of old links in i915_gem_object_attach_phys()
v3.1: Fix the fix, only unlink if it was linked
v3.2: Use a local for to_i915(obj->base.dev)->mm.obj_lock

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171016114037.5556-1-chris@chris-wilson.co.uk

1 files changed, 3 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
index 473aa9631145..f463105ff48d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_evict.c
@@ -50,7 +50,7 @@ static int populate_ggtt(struct drm_i915_private *i915)
 
 	if (!list_empty(&i915->mm.unbound_list)) {
 		size = 0;
-		list_for_each_entry(obj, &i915->mm.unbound_list, global_link)
+		list_for_each_entry(obj, &i915->mm.unbound_list, mm.link)
 			size++;
 
 		pr_err("Found %lld objects unbound!\n", size);
@@ -77,10 +77,10 @@ static void cleanup_objects(struct drm_i915_private *i915)
 {
 	struct drm_i915_gem_object *obj, *on;
 
-	list_for_each_entry_safe(obj, on, &i915->mm.unbound_list, global_link)
+	list_for_each_entry_safe(obj, on, &i915->mm.unbound_list, mm.link)
 		i915_gem_object_put(obj);
 
-	list_for_each_entry_safe(obj, on, &i915->mm.bound_list, global_link)
+	list_for_each_entry_safe(obj, on, &i915->mm.bound_list, mm.link)
 		i915_gem_object_put(obj);
 
 	mutex_unlock(&i915->drm.struct_mutex);
@@ -152,8 +152,6 @@ static int igt_overcommit(void *arg)
 		goto cleanup;
 	}
 
-	list_move(&obj->global_link, &i915->mm.unbound_list);
-
 	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, 0);
 	if (!IS_ERR(vma) || PTR_ERR(vma) != -ENOSPC) {
 		pr_err("Failed to evict+insert, i915_gem_object_ggtt_pin returned err=%d\n", (int)PTR_ERR(vma));