Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754704Ab3GOJer (ORCPT ); Mon, 15 Jul 2013 05:34:47 -0400 Received: from mail-la0-f41.google.com ([209.85.215.41]:61798 "EHLO mail-la0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754547Ab3GOJeo (ORCPT ); Mon, 15 Jul 2013 05:34:44 -0400 From: Ricardo Ribalda Delgado To: Pawel Osciak , Marek Szyprowski , Kyungmin Park , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org (open list) Cc: Ricardo Ribalda Delgado Subject: [PATCH] videobuf2-dma-sg: Minimize the number of dma segments Date: Mon, 15 Jul 2013 11:34:34 +0200 Message-Id: <1373880874-9270-1-git-send-email-ricardo.ribalda@gmail.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3163 Lines: 102 Most DMA engines have limitations regarding the number of DMA segments (sg-buffers) that they can handle. Videobuffers can easily spread through houndreds 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_exact. In the worst case it will behave as before, but most of the times it will reduce the number fo dma segments Signed-off-by: Ricardo Ribalda Delgado --- drivers/media/v4l2-core/videobuf2-dma-sg.c | 49 +++++++++++++++++++++------- 1 file changed, 38 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..67a94ab 100644 --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c @@ -42,10 +42,44 @@ 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; + void *vaddr = NULL; + unsigned int req_pages; + + while (last_page < buf->sg_desc.num_pages) { + req_pages = buf->sg_desc.num_pages-last_page; + while (req_pages >= 1) { + vaddr = alloc_pages_exact(req_pages*PAGE_SIZE, + GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN); + if (vaddr) + break; + req_pages >>= 1; + } + if (!vaddr) { + while (--last_page >= 0) + __free_page(buf->pages[last_page]); + return -ENOMEM; + } + while (req_pages) { + buf->pages[last_page] = virt_to_page(vaddr); + sg_set_page(&buf->sg_desc.sglist[last_page], + buf->pages[last_page], PAGE_SIZE, 0); + vaddr += PAGE_SIZE; + last_page++; + req_pages--; + } + } + + 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 +103,9 @@ 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 +118,6 @@ 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: -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/