Attempt to document shrink_pin and the other relevant interfaces that interact with it, before we start messing with it.
Signed-off-by: Matthew Auld matthew.auld@intel.com Cc: Thomas Hellström thomas.hellstrom@linux.intel.com Reviewed-by: Thomas Hellström thomas.hellstrom@linux.intel.com --- .../gpu/drm/i915/gem/i915_gem_object_types.h | 24 +++++++++++++- drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 31 +++++++++++++++++++ 2 files changed, 54 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h index 7dd5f804aab3..f4233c4e8d2e 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h @@ -461,6 +461,28 @@ struct drm_i915_gem_object { * instead go through the pin/unpin interfaces. */ atomic_t pages_pin_count; + + /** + * @shrink_pin: Prevents the pages from being made visible to + * the shrinker, while the shrink_pin is non-zero. Most users + * should pretty much never have to care about this, outside of + * some special use cases. + * + * By default most objects will start out as visible to the + * shrinker(if I915_GEM_OBJECT_IS_SHRINKABLE) as soon as the + * backing pages are attached to the object, like in + * __i915_gem_object_set_pages(). They will then be removed the + * shrinker list once the pages are released. + * + * The @shrink_pin is incremented by calling + * i915_gem_object_make_unshrinkable(), which will also remove + * the object from the shrinker list, if the pin count was zero. + * + * Callers will then typically call + * i915_gem_object_make_shrinkable() or + * i915_gem_object_make_purgeable() to decrement the pin count, + * and make the pages visible again. + */ atomic_t shrink_pin;
/** @@ -522,7 +544,7 @@ struct drm_i915_gem_object { struct i915_gem_object_page_iter get_dma_page;
/** - * Element within i915->mm.unbound_list or i915->mm.bound_list, + * Element within i915->mm.shrink_list or i915->mm.purge_list, * locked by i915->mm.obj_lock. */ struct list_head link; diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c index ae2a8d54b7a4..66121fedc655 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c @@ -463,6 +463,16 @@ void i915_gem_shrinker_taints_mutex(struct drm_i915_private *i915,
#define obj_to_i915(obj__) to_i915((obj__)->base.dev)
+/** + * i915_gem_object_make_unshrinkable - Hide the object from the shrinker. By + * default all object types that support shrinking(see IS_SHRINKABLE), will also + * make the object visible to the shrinker after allocating the system memory + * pages. + * @obj: The GEM object. + * + * This is typically used for special kernel internal objects that can't be + * easily processed by the shrinker, like if they are perma-pinned. + */ void i915_gem_object_make_unshrinkable(struct drm_i915_gem_object *obj) { struct drm_i915_private *i915 = obj_to_i915(obj); @@ -513,12 +523,33 @@ static void __i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj, spin_unlock_irqrestore(&i915->mm.obj_lock, flags); }
+/** + * i915_gem_object_make_shrinkable - Move the object to the tail of the + * shrinkable list. Objects on this list might be swapped out. Used with + * WILLNEED objects. + * @obj: The GEM object. + * + * MUST only be called on objects which have backing pages. + * + * MUST be balanced with previous call to i915_gem_object_make_unshrinkable(). + */ void i915_gem_object_make_shrinkable(struct drm_i915_gem_object *obj) { __i915_gem_object_make_shrinkable(obj, &obj_to_i915(obj)->mm.shrink_list); }
+/** + * i915_gem_object_make_purgeable - Move the object to the tail of the purgeable + * list. Used with DONTNEED objects. Unlike with shrinkable objects, the + * shrinker will attempt to discard the backing pages, instead of trying to swap + * them out. + * @obj: The GEM object. + * + * MUST only be called on objects which have backing pages. + * + * MUST be balanced with previous call to i915_gem_object_make_unshrinkable(). + */ void i915_gem_object_make_purgeable(struct drm_i915_gem_object *obj) { __i915_gem_object_make_shrinkable(obj,