From df23728118cd0f53070769e2ac26a255f66daa57 Mon Sep 17 00:00:00 2001 From: Ricardo Ribalda Date: Fri, 2 Aug 2013 10:19:59 -0300 Subject: [PATCH] [media] videobuf2-dma-sg: Allocate pages as contiguous as possible Most DMA engines have limitations regarding the number of DMA segments (sg-buffers) that they can handle. Videobuffers can easily spread through hundreds of pages. In the previous aproach, the pages were allocated individually, this could led to the creation houndreds of dma segments (sg-buffers) that could not be handled by some DMA engines. This patch tries to minimize the number of DMA segments by using alloc_pages. In the worst case it will behave as before, but most of the times it will reduce the number of dma segments Acked-by: Marek Szyprowski Reviewed-by: Andre Heider Signed-off-by: Ricardo Ribalda Delgado Signed-off-by: Sylwester Nawrocki Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/videobuf2-dma-sg.c | 60 ++++++++++++++++++++++++------ 1 file changed, 49 insertions(+), 11 deletions(-) diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c index 16ae3dc..4999c48 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c @@ -42,10 +42,55 @@ struct vb2_dma_sg_buf { static void vb2_dma_sg_put(void *buf_priv); +static int vb2_dma_sg_alloc_compacted(struct vb2_dma_sg_buf *buf, + gfp_t gfp_flags) +{ + unsigned int last_page = 0; + int size = buf->sg_desc.size; + + while (size > 0) { + struct page *pages; + int order; + int i; + + order = get_order(size); + /* Dont over allocate*/ + if ((PAGE_SIZE << order) > size) + order--; + + pages = NULL; + while (!pages) { + pages = alloc_pages(GFP_KERNEL | __GFP_ZERO | + __GFP_NOWARN | gfp_flags, order); + if (pages) + break; + + if (order == 0) { + while (last_page--) + __free_page(buf->pages[last_page]); + return -ENOMEM; + } + order--; + } + + split_page(pages, order); + for (i = 0; i < (1 << order); i++) { + buf->pages[last_page] = &pages[i]; + sg_set_page(&buf->sg_desc.sglist[last_page], + buf->pages[last_page], PAGE_SIZE, 0); + last_page++; + } + + size -= PAGE_SIZE << order; + } + + return 0; +} + static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_flags) { struct vb2_dma_sg_buf *buf; - int i; + int ret; buf = kzalloc(sizeof *buf, GFP_KERNEL); if (!buf) @@ -69,14 +114,9 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_fla if (!buf->pages) goto fail_pages_array_alloc; - for (i = 0; i < buf->sg_desc.num_pages; ++i) { - buf->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO | - __GFP_NOWARN | gfp_flags); - if (NULL == buf->pages[i]) - goto fail_pages_alloc; - sg_set_page(&buf->sg_desc.sglist[i], - buf->pages[i], PAGE_SIZE, 0); - } + ret = vb2_dma_sg_alloc_compacted(buf, gfp_flags); + if (ret) + goto fail_pages_alloc; buf->handler.refcount = &buf->refcount; buf->handler.put = vb2_dma_sg_put; @@ -89,8 +129,6 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_fla return buf; fail_pages_alloc: - while (--i >= 0) - __free_page(buf->pages[i]); kfree(buf->pages); fail_pages_array_alloc: -- 2.7.4