Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b338fa47 authored by Dave Gordon's avatar Dave Gordon Committed by Chris Wilson
Browse files

drm/i915: optimise i915_gem_object_map() for small objects 



We're using this function for ringbuffers and other "small" objects, so
it's worth avoiding an extra malloc()/free() cycle if the page array is
small enough to put on the stack. Here we've chosen an arbitrary cutoff
of 32 (4k) pages, which is big enough for a ringbuffer (4 pages) or a
context image (currently up to 22 pages).

v5:
    change name of local array [Chris Wilson]

Signed-off-by: default avatarDave Gordon <david.s.gordon@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1463741647-15666-3-git-send-email-chris@chris-wilson.co.uk
parent dd6034c6

drivers/gpu/drm/i915/i915_gem.c

+10 −5
Original line number Original line Diff line number Diff line
@@ -2404,7 +2404,8 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) 
	unsigned long n_pages = obj->base.size >> PAGE_SHIFT;

	unsigned long n_pages = obj->base.size >> PAGE_SHIFT;

	struct sg_table *sgt = obj->pages;

	struct sg_table *sgt = obj->pages;

	struct sg_page_iter sg_iter;

	struct sg_page_iter sg_iter;

	struct page **pages;

	struct page *stack_pages[32];

	struct page **pages = stack_pages;

	unsigned long i = 0;

	unsigned long i = 0;

	void *addr;

	void *addr;
@@ -2412,9 +2413,12 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) 
	if (n_pages == 1)

	if (n_pages == 1)

		return kmap(sg_page(sgt->sgl));

		return kmap(sg_page(sgt->sgl));





	if (n_pages > ARRAY_SIZE(stack_pages)) {

		/* Too big for stack -- allocate temporary array instead */

		pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY);

		pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY);

		if (!pages)

		if (!pages)

			return NULL;

			return NULL;

	}





	for_each_sg_page(sgt->sgl, &sg_iter, sgt->nents, 0)

	for_each_sg_page(sgt->sgl, &sg_iter, sgt->nents, 0)

		pages[i++] = sg_page_iter_page(&sg_iter);

		pages[i++] = sg_page_iter_page(&sg_iter);
@@ -2424,6 +2428,7 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) 




	addr = vmap(pages, n_pages, 0, PAGE_KERNEL);

	addr = vmap(pages, n_pages, 0, PAGE_KERNEL);





	if (pages != stack_pages)

		drm_free_large(pages);

		drm_free_large(pages);





	return addr;

	return addr;