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 <david.s.gor...@intel.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com> Cc: Chris Wilson <ch...@chris-wilson.co.uk> --- drivers/gpu/drm/i915/i915_gem.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index fc42be0..71667bc 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2402,7 +2402,8 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) unsigned long n_pages = obj->base.size >> PAGE_SHIFT; struct scatterlist *sg = obj->pages->sgl; 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 = NULL; @@ -2410,10 +2411,13 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) if (n_pages == 1) return kmap(sg_page(sg)); - pages = drm_malloc_gfp(n_pages, sizeof(*pages), GFP_TEMPORARY); - if (pages == NULL) { - DRM_DEBUG_DRIVER("Failed to get space for pages\n"); - 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 == NULL) { + DRM_DEBUG_DRIVER("Failed to get space for pages\n"); + return NULL; + } } for_each_sg_page(sg, &sg_iter, n_pages, 0) { @@ -2429,7 +2433,8 @@ static void *i915_gem_object_map(const struct drm_i915_gem_object *obj) if (addr == NULL) DRM_DEBUG_DRIVER("Failed to vmap pages\n"); - drm_free_large(pages); + if (pages != stack_pages) + drm_free_large(pages); return addr; } -- 1.9.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx