From: Tvrtko Ursulin <tvrtko.ursu...@intel.com> With the current way of allocating backing store which over-estimates the number of sg entries required we typically waste around 1-6 MiB of memory on unused sg entries at runtime.
We can instead have the intermediate step of storing our pages in an array and use __sg_alloc_table_from_pages which will create us the most compact list possible. Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com> --- drivers/gpu/drm/i915/i915_gem.c | 72 ++++++++++++++++++++--------------------- 1 file changed, 35 insertions(+), 37 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 8ed8e24025ac..4bf675568a37 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2208,9 +2208,9 @@ i915_gem_object_put_pages(struct drm_i915_gem_object *obj) static unsigned int swiotlb_max_size(void) { #if IS_ENABLED(CONFIG_SWIOTLB) - return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE); + return swiotlb_nr_tbl() << IO_TLB_SHIFT; #else - return 0; + return UINT_MAX; #endif } @@ -2221,11 +2221,8 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) int page_count, i; struct address_space *mapping; struct sg_table *st; - struct scatterlist *sg; - struct sgt_iter sgt_iter; - struct page *page; - unsigned long last_pfn = 0; /* suppress gcc warning */ - unsigned int max_segment; + struct page *page, **pages; + unsigned int max_segment = swiotlb_max_size(); int ret; gfp_t gfp; @@ -2236,18 +2233,16 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS); BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS); - max_segment = swiotlb_max_size(); - if (!max_segment) - max_segment = rounddown(UINT_MAX, PAGE_SIZE); - - st = kmalloc(sizeof(*st), GFP_KERNEL); - if (st == NULL) - return -ENOMEM; - page_count = obj->base.size / PAGE_SIZE; - if (sg_alloc_table(st, page_count, GFP_KERNEL)) { - kfree(st); + pages = drm_malloc_gfp(page_count, sizeof(struct page *), + GFP_TEMPORARY | __GFP_ZERO); + if (!pages) return -ENOMEM; + + st = kmalloc(sizeof(*st), GFP_KERNEL); + if (st == NULL) { + ret = -ENOMEM; + goto err_st; } /* Get the list of pages out of our struct file. They'll be pinned @@ -2258,8 +2253,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) mapping = obj->base.filp->f_mapping; gfp = mapping_gfp_constraint(mapping, ~(__GFP_IO | __GFP_RECLAIM)); gfp |= __GFP_NORETRY | __GFP_NOWARN; - sg = st->sgl; - st->nents = 0; for (i = 0; i < page_count; i++) { page = shmem_read_mapping_page_gfp(mapping, i, gfp); if (IS_ERR(page)) { @@ -2281,29 +2274,28 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) goto err_pages; } } - if (!i || - sg->length >= max_segment || - page_to_pfn(page) != last_pfn + 1) { - if (i) - sg = sg_next(sg); - st->nents++; - sg_set_page(sg, page, PAGE_SIZE, 0); - } else { - sg->length += PAGE_SIZE; - } - last_pfn = page_to_pfn(page); + + pages[i] = page; /* Check that the i965g/gm workaround works. */ - WARN_ON((gfp & __GFP_DMA32) && (last_pfn >= 0x00100000UL)); + WARN_ON((gfp & __GFP_DMA32) && + (page_to_pfn(page) >= 0x00100000UL)); } - if (sg) /* loop terminated early; short sg table */ - sg_mark_end(sg); + + ret = __sg_alloc_table_from_pages(st, pages, page_count, 0, + obj->base.size, GFP_KERNEL, + max_segment); + if (ret) + goto err_pages; + obj->pages = st; ret = i915_gem_gtt_prepare_object(obj); if (ret) goto err_pages; + drm_free_large(pages); + if (i915_gem_object_needs_bit17_swizzle(obj)) i915_gem_object_do_bit_17_swizzle(obj); @@ -2314,10 +2306,13 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) return 0; err_pages: - sg_mark_end(sg); - for_each_sgt_page(page, sgt_iter, st) - put_page(page); - sg_free_table(st); + for (i = 0; i < page_count; i++) { + if (pages[i]) + put_page(pages[i]); + else + break; + } + kfree(st); /* shmemfs first checks if there is enough memory to allocate the page @@ -2331,6 +2326,9 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj) if (ret == -ENOSPC) ret = -ENOMEM; +err_st: + drm_free_large(pages); + return ret; } -- 2.7.4