On 29/02/16 11:13, Dave Gordon wrote:
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.gordon@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Alex Dai <yu.dai@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
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 c621b3e..c126211 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2417,7 +2417,8 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj,
unsigned int npages)
{
struct sg_page_iter sg_iter;
- struct page **pages;
+ struct page *stack_pages[32];
+ struct page **pages = stack_pages;
void *addr;
int i;
@@ -2426,10 +2427,13 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj,
return NULL;
}
- pages = drm_malloc_gfp(npages, sizeof(*pages), GFP_TEMPORARY);
- if (pages == NULL) {
- DRM_DEBUG_DRIVER("Failed to get space for pages\n");
- return NULL;
+ if (npages > ARRAY_SIZE(stack_pages)) {
+ /* Too big for stack -- allocate temporary array instead */
+ pages = drm_malloc_gfp(npages, sizeof(*pages), GFP_TEMPORARY);
+ if (pages == NULL) {
+ DRM_DEBUG_DRIVER("Failed to get space for pages\n");
+ return NULL;
+ }
}
i = 0;
@@ -2442,7 +2446,8 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj,
addr = vmap(pages, npages, 0, PAGE_KERNEL);
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;
}
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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