From mboxrd@z Thu Jan 1 00:00:00 1970 From: Govindarajulu Varadarajan <_govind@gmx.com> Subject: [PATCH net-next v3 0/2] introduce dma frag allocation and reduce dma mapping Date: Tue, 10 Mar 2015 23:13:02 +0530 Message-ID: <1426009384-11544-1-git-send-email-_govind@gmx.com> Cc: ssujith@cisco.com, benve@cisco.com, Govindarajulu Varadarajan <_govind@gmx.com> To: davem@davemloft.net, netdev@vger.kernel.org Return-path: Received: from mout.gmx.net ([212.227.15.19]:56860 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752765AbbCJRnZ (ORCPT ); Tue, 10 Mar 2015 13:43:25 -0400 Sender: netdev-owner@vger.kernel.org List-ID: The following series tries to address these two problem in dma buff allocation. * Memory wastage because of large 9k allocation using kmalloc: For 9k dma buffer, netdev_alloc_skb_ip_align internally calls kmalloc for size > 4096. In case of 9k buff, kmalloc returns pages for order 2, 16k. And we use only ~9k of 16k. 7k memory wasted. Using the frag the frag allocator in patch 1/2, we can allocate three 9k buffs in a 32k page size. Typical enic configuration has 8 rq, and desc ring of size 4096. Thats 8 * 4096 * (16*1024) = 512 MB. Using this frag allocator: 8 * 4096 * (32*1024/3) = 341 MB. Thats 171 MB of memory save. * frequent dma_map() calls: we call dma_map() for every buff we allocate. When iommu is on, This is very time consuming. From my testing, most of the cpu cycles are wasted spinning on spin_lock_irqsave(&iovad->iova_rbtree_lock, flags) in intel_map_page() .. -> ..__alloc_and_insert_iova_range() With this patch, we call dma_map() once for 32k page. i.e once for every three 9k desc, and once every twenty 1500 bytes desc. Here are my testing result with 8 rq, 4096 ring size and 9k mtu. irq of each rq is affinitized with different CPU. Ran iperf with 32 threads. Link is 10G. iommu is on. CPU utilization throughput without patch 100% 1.8 Gbps with patch 13% 9.8 Gbps v3: Make this facility more generic so that other drivers can use it. v2: Remove changing order facility Govindarajulu Varadarajan (2): net: implement dma cache skb allocator enic: use netdev_dma_alloc drivers/net/ethernet/cisco/enic/enic_main.c | 31 ++--- drivers/net/ethernet/cisco/enic/vnic_rq.c | 3 + drivers/net/ethernet/cisco/enic/vnic_rq.h | 3 + include/linux/skbuff.h | 22 +++ net/core/skbuff.c | 209 ++++++++++++++++++++++++++++ 5 files changed, 246 insertions(+), 22 deletions(-) -- 2.3.2