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
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