drm/i915: Replace a calloc followed by copying data over it with malloc.

Execbufs involve quite a bit of payload, to the extent that cache misses
show up in the profiles here, and a suspicion that some of those cachelines
may get evicted and then reloaded in the subsequent copy.

This is still abstracted like drm_calloc_large since we want to check for
size overflow, and because we want to choose between kmalloc and vmalloc
on the fly.  cairo's interface for malloc-with-calloc's-args was used as
the model.

Signed-off-by: Eric Anholt <eric@anholt.net>

2 files changed, 16 insertions, 3 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 2065b8f7e875..481c0ab888c8 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3563,8 +3563,8 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
                 return -EINVAL;
         }
         /* Copy in the exec list from userland */
-        exec_list = drm_calloc_large(sizeof(*exec_list), args->buffer_count);
-        object_list = drm_calloc_large(sizeof(*object_list), args->buffer_count);
+        exec_list = drm_malloc_ab(sizeof(*exec_list), args->buffer_count);
+        object_list = drm_malloc_ab(sizeof(*object_list), args->buffer_count);
         if (exec_list == NULL || object_list == NULL) {
                 DRM_ERROR("Failed to allocate exec or object list "
                           "for %d buffers\n",
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index b0b36838ab11..1b807d0f6cdb 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1545,14 +1545,27 @@ static __inline__ void drm_core_dropmap(struct drm_local_map *map)
 
 static __inline__ void *drm_calloc_large(size_t nmemb, size_t size)
 {
+        if (size != 0 && nmemb > ULONG_MAX / size)
+                return NULL;
+
         if (size * nmemb <= PAGE_SIZE)
             return kcalloc(nmemb, size, GFP_KERNEL);
 
+        return __vmalloc(size * nmemb,
+                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
+}
+
+/* Modeled after cairo's malloc_ab, it's like calloc but without the zeroing. */
+static __inline__ void *drm_malloc_ab(size_t nmemb, size_t size)
+{
         if (size != 0 && nmemb > ULONG_MAX / size)
                 return NULL;
 
+        if (size * nmemb <= PAGE_SIZE)
+            return kmalloc(nmemb * size, GFP_KERNEL);
+
         return __vmalloc(size * nmemb,
-                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
+                         GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
 }
 
 static __inline void drm_free_large(void *ptr)