[PATCH 2/2] drm/i915: Mark pinned shmemfs pages as unevictable

[Kuo-Hsin Yang <vovoy@chromium.org>]

The i915 driver use shmemfs to allocate backing storage for gem objects.
These shmemfs pages can be pinned (increased ref count) by
shmem_read_mapping_page_gfp(). When a lot of pages are pinned, vmscan
wastes a lot of time scanning these pinned pages. Mark these pinned
pages as unevictable to speed up vmscan.

Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
---
 drivers/gpu/drm/i915/i915_gem.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fcc73a6ab503..e0ff5b736128 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2390,6 +2390,7 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 {
 	struct sgt_iter sgt_iter;
 	struct page *page;
+	struct address_space *mapping;
 
 	__i915_gem_object_release_shmem(obj, pages, true);
 
@@ -2409,6 +2410,10 @@ i915_gem_object_put_pages_gtt(struct drm_i915_gem_object *obj,
 	}
 	obj->mm.dirty = false;
 
+	mapping = file_inode(obj->base.filp)->i_mapping;
+	mapping_clear_unevictable(mapping);
+	shmem_unlock_mapping(mapping);
+
 	sg_free_table(pages);
 	kfree(pages);
 }
@@ -2551,6 +2556,7 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 	 * Fail silently without starting the shrinker
 	 */
 	mapping = obj->base.filp->f_mapping;
+	mapping_set_unevictable(mapping);
 	noreclaim = mapping_gfp_constraint(mapping, ~__GFP_RECLAIM);
 	noreclaim |= __GFP_NORETRY | __GFP_NOWARN;
 
@@ -2664,6 +2670,8 @@ static int i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 err_pages:
 	for_each_sgt_page(page, sgt_iter, st)
 		put_page(page);
+	mapping_clear_unevictable(mapping);
+	shmem_unlock_mapping(mapping);
 	sg_free_table(st);
 	kfree(st);
 
-- 
2.19.1.331.ge82ca0e54c-goog