| Message ID | 1456154308-9342-4-git-send-email-david.s.gordon@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Feb 22, 2016 at 03:18:28PM +0000, Dave Gordon wrote: > Now that we use this function for ringbuffers and other "small" objects, > it's worth avoiding an extra kmalloc()/kfree() 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). > > Signed-off-by: Dave Gordon <david.s.gordon@intel.com> > Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> > Cc: Alex Dai <yu.dai@intel.com> > Cc: Chris Wilson <chris@chris-wilson.co.uk> > --- > drivers/gpu/drm/i915/i915_gem.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > index 14942cf..effb69b 100644 > --- a/drivers/gpu/drm/i915/i915_gem.c > +++ b/drivers/gpu/drm/i915/i915_gem.c > @@ -2422,6 +2422,7 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj, > unsigned int npages) > { > struct sg_page_iter sg_iter; > + struct page *mypages[32]; Use stack or stack_pages, that's the pattern we've used elsewhere. Though pages_on_stack would be more in line with the rest of the kernel. > struct page **pages; > void *addr; > int i; > @@ -2431,10 +2432,16 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj, > return NULL; > } > > - pages = drm_malloc_ab(npages, sizeof(*pages)); > - if (pages == NULL) { > - DRM_DEBUG_DRIVER("Failed to get space for pages\n"); > - return NULL; > + if (npages <= ARRAY_SIZE(mypages)) > + pages = mypages; If one branch requires braces, add them to all. > + else { > + pages = kmalloc(npages*sizeof(*pages), GFP_TEMPORARY | __GFP_NOWARN); drm_malloc_gfp Otherwise, seems an ok idea. The deepest vmap is the ioctl/execbuffer/cmdparser to which using a further 256 bytes of stack is acceptable. -Chris
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 14942cf..effb69b 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2422,6 +2422,7 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj, unsigned int npages) { struct sg_page_iter sg_iter; + struct page *mypages[32]; struct page **pages; void *addr; int i; @@ -2431,10 +2432,16 @@ void *i915_gem_object_vmap_range(struct drm_i915_gem_object *obj, return NULL; } - pages = drm_malloc_ab(npages, sizeof(*pages)); - if (pages == NULL) { - DRM_DEBUG_DRIVER("Failed to get space for pages\n"); - return NULL; + if (npages <= ARRAY_SIZE(mypages)) + pages = mypages; + else { + pages = kmalloc(npages*sizeof(*pages), GFP_TEMPORARY | __GFP_NOWARN); + if (pages == NULL) + pages = drm_malloc_ab(npages, sizeof(*pages)); + if (pages == NULL) { + DRM_DEBUG_DRIVER("Failed to get space for pages\n"); + return NULL; + } } i = 0; @@ -2447,7 +2454,8 @@ 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 != mypages) + drm_free_large(pages); return addr; }
Now that we use this function for ringbuffers and other "small" objects, it's worth avoiding an extra kmalloc()/kfree() 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). Signed-off-by: Dave Gordon <david.s.gordon@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Alex Dai <yu.dai@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> --- drivers/gpu/drm/i915/i915_gem.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)