The biggest user of i915_gem_object_get_page() is the relocation processing during execbuffer. Typically userspace passes in a set of relocations in sorted order. Sadly, we alternate between relocations increasing from the start of the buffers, and relocations decreasing from the end. However the majority of consecutive lookups will still be in the same page. We could cache the start of the last sg chain, however for most callers, the entire sgl is inside a single chain and so we see no improve from the extra layer of caching. v2: Avoid the double increment inside unlikely() References: https://bugs.freedesktop.org/show_bug.cgi?id=88308 Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Cc: John Harrison <John.C.Harrison@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_drv.h | 31 ++++++++++++++++++++++++++----- drivers/gpu/drm/i915/i915_gem.c | 4 ++++ 2 files changed, 30 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 9490403db23a..701079429832 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1985,6 +1985,10 @@ struct drm_i915_gem_object { struct sg_table *pages; int pages_pin_count; + struct get_page { + struct scatterlist *sg; + int last; + } get_page; /* prime dma-buf support */ void *dma_buf_vmapping; @@ -2642,15 +2646,32 @@ int i915_gem_obj_prepare_shmem_read(struct drm_i915_gem_object *obj, int *needs_clflush); int __must_check i915_gem_object_get_pages(struct drm_i915_gem_object *obj); -static inline struct page *i915_gem_object_get_page(struct drm_i915_gem_object *obj, int n) + +static inline int __sg_page_count(struct scatterlist *sg) +{ + return sg->length >> PAGE_SHIFT; +} + +static inline struct page * +i915_gem_object_get_page(struct drm_i915_gem_object *obj, int n) { - struct sg_page_iter sg_iter; + if (WARN_ON(n >= obj->base.size >> PAGE_SHIFT)) + return NULL; - for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, n) - return sg_page_iter_page(&sg_iter); + if (n < obj->get_page.last) { + obj->get_page.sg = obj->pages->sgl; + obj->get_page.last = 0; + } + + while (obj->get_page.last + __sg_page_count(obj->get_page.sg) <= n) { + obj->get_page.last += __sg_page_count(obj->get_page.sg++); + if (unlikely(sg_is_chain(obj->get_page.sg))) + obj->get_page.sg = sg_chain_ptr(obj->get_page.sg); + } - return NULL; + return nth_page(sg_page(obj->get_page.sg), n - obj->get_page.last); } + static inline void i915_gem_object_pin_pages(struct drm_i915_gem_object *obj) { BUG_ON(obj->pages == NULL); diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index c4762d58e97a..476687a9d067 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2178,6 +2178,10 @@ i915_gem_object_get_pages(struct drm_i915_gem_object *obj) return ret; list_add_tail(&obj->global_list, &dev_priv->mm.unbound_list); + + obj->get_page.sg = obj->pages->sgl; + obj->get_page.last = 0; + return 0; } -- 2.1.4 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
