From b338fa473e16c9be208b0aec7ec4e710a8a5f9ee Mon Sep 17 00:00:00 2001 From: Dave Gordon Date: Fri, 20 May 2016 11:54:05 +0100 Subject: [PATCH] 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: Dave Gordon Reviewed-by: Tvrtko Ursulin Reviewed-by: Chris Wilson Signed-off-by: Chris Wilson Link: http://patchwork.freedesktop.org/patch/msgid/1463741647-15666-3-git-send-email-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index f504c3168da5..fd3be2b385cb 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -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; struct sg_table *sgt = obj->pages; struct sg_page_iter sg_iter; - struct page **pages; + struct page *stack_pages[32]; + struct page **pages = stack_pages; unsigned long i = 0; void *addr; @@ -2412,9 +2413,12 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) if (n_pages == 1) return kmap(sg_page(sgt->sgl)); - pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY); - if (!pages) - return NULL; + 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); + if (!pages) + return NULL; + } for_each_sg_page(sgt->sgl, &sg_iter, sgt->nents, 0) pages[i++] = sg_page_iter_page(&sg_iter); @@ -2424,7 +2428,8 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) addr = vmap(pages, n_pages, 0, PAGE_KERNEL); - drm_free_large(pages); + if (pages != stack_pages) + drm_free_large(pages); return addr; } -- 2.39.5