drm/i915: Micro-optimise i915_get_ggtt_vma_pages()

The predominant VMA class is normal GTT, so allow gcc to emphasize that
path and avoid unnecessary stack movement.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170215084357.19977-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index cb5ea5d..ae04b6e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -2621,14 +2621,16 @@ static int ggtt_bind_vma(struct i915_vma *vma,
 {
        struct drm_i915_private *i915 = vma->vm->i915;
        struct drm_i915_gem_object *obj = vma->obj;
-       u32 pte_flags = 0;
-       int ret;
+       u32 pte_flags;
 
-       ret = i915_get_ggtt_vma_pages(vma);
-       if (ret)
-               return ret;
+       if (unlikely(!vma->pages)) {
+               int ret = i915_get_ggtt_vma_pages(vma);
+               if (ret)
+                       return ret;
+       }
 
        /* Currently applicable only to VLV */
+       pte_flags = 0;
        if (obj->gt_ro)
                pte_flags |= PTE_READ_ONLY;
 
@@ -2653,18 +2655,18 @@ static int aliasing_gtt_bind_vma(struct i915_vma *vma,
 {
        struct drm_i915_private *i915 = vma->vm->i915;
        u32 pte_flags;
-       int ret;
 
-       ret = i915_get_ggtt_vma_pages(vma);
-       if (ret)
-               return ret;
+       if (unlikely(!vma->pages)) {
+               int ret = i915_get_ggtt_vma_pages(vma);
+               if (ret)
+                       return ret;
+       }
 
        /* Currently applicable only to VLV */
        pte_flags = 0;
        if (vma->obj->gt_ro)
                pte_flags |= PTE_READ_ONLY;
 
-
        if (flags & I915_VMA_GLOBAL_BIND) {
                intel_runtime_pm_get(i915);
                vma->vm->insert_entries(vma->vm,
@@ -3430,9 +3432,9 @@ rotate_pages(const dma_addr_t *in, unsigned int offset,
        return sg;
 }
 
-static struct sg_table *
-intel_rotate_fb_obj_pages(const struct intel_rotation_info *rot_info,
-                         struct drm_i915_gem_object *obj)
+static noinline struct sg_table *
+intel_rotate_pages(struct intel_rotation_info *rot_info,
+                  struct drm_i915_gem_object *obj)
 {
        const size_t n_pages = obj->base.size / PAGE_SIZE;
        unsigned int size = intel_rotation_info_size(rot_info);
@@ -3493,7 +3495,7 @@ err_st_alloc:
        return ERR_PTR(ret);
 }
 
-static struct sg_table *
+static noinline struct sg_table *
 intel_partial_pages(const struct i915_ggtt_view *view,
                    struct drm_i915_gem_object *obj)
 {
@@ -3547,7 +3549,7 @@ err_st_alloc:
 static int
 i915_get_ggtt_vma_pages(struct i915_vma *vma)
 {
-       int ret = 0;
+       int ret;
 
        /* The vma->pages are only valid within the lifespan of the borrowed
         * obj->mm.pages. When the obj->mm.pages sg_table is regenerated, so
@@ -3556,32 +3558,33 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
         */
        GEM_BUG_ON(!i915_gem_object_has_pinned_pages(vma->obj));
 
-       if (vma->pages)
+       switch (vma->ggtt_view.type) {
+       case I915_GGTT_VIEW_NORMAL:
+               vma->pages = vma->obj->mm.pages;
                return 0;
 
-       if (vma->ggtt_view.type == I915_GGTT_VIEW_NORMAL)
-               vma->pages = vma->obj->mm.pages;
-       else if (vma->ggtt_view.type == I915_GGTT_VIEW_ROTATED)
+       case I915_GGTT_VIEW_ROTATED:
                vma->pages =
-                       intel_rotate_fb_obj_pages(&vma->ggtt_view.rotated,
-                                                 vma->obj);
-       else if (vma->ggtt_view.type == I915_GGTT_VIEW_PARTIAL)
+                       intel_rotate_pages(&vma->ggtt_view.rotated, vma->obj);
+               break;
+
+       case I915_GGTT_VIEW_PARTIAL:
                vma->pages = intel_partial_pages(&vma->ggtt_view, vma->obj);
-       else
+               break;
+
+       default:
                WARN_ONCE(1, "GGTT view %u not implemented!\n",
                          vma->ggtt_view.type);
+               return -EINVAL;
+       }
 
-       if (!vma->pages) {
-               DRM_ERROR("Failed to get pages for GGTT view type %u!\n",
-                         vma->ggtt_view.type);
-               ret = -EINVAL;
-       } else if (IS_ERR(vma->pages)) {
+       ret = 0;
+       if (unlikely(IS_ERR(vma->pages))) {
                ret = PTR_ERR(vma->pages);
                vma->pages = NULL;
                DRM_ERROR("Failed to get pages for VMA view type %u (%d)!\n",
                          vma->ggtt_view.type, ret);
        }
-
        return ret;
 }