Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933179Ab1EZUAb (ORCPT ); Thu, 26 May 2011 16:00:31 -0400 Received: from e8.ny.us.ibm.com ([32.97.182.138]:39258 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933118Ab1EZUAZ (ORCPT ); Thu, 26 May 2011 16:00:25 -0400 Subject: [PATCH V6 0/4 net-next] macvtap/vhost TX zero-copy support From: Shirley Ma To: David Miller , mst@redhat.com, Eric Dumazet , Avi Kivity , Arnd Bergmann Cc: netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Date: Thu, 26 May 2011 13:00:20 -0700 Message-ID: <1306440020.5180.47.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4147 Lines: 103 This patchset add supports for TX zero-copy between guest and host kernel through vhost. It significantly reduces CPU utilization on the local host on which the guest is located (It reduced about 50% CPU usage for single stream test on the host, while 4K message size BW has increased about 50%). The patchset is based on previous submission and comments from the community regarding when/how to handle guest kernel buffers to be released. This is the simplest approach I can think of after comparing with several other solutions. This patchset has integrated V3 review comments from community: 1. Add more comments on how to use device ZEROCOPY flag; 2. Change device ZEROCOPY to available bit 31 3. Fix skb header linear allocation when virtio_net GSO is not enabled It has integrated V4 review comments from MST and Sridhar: 1. In vhost, using socket poll wake up for outstanding DMAs 2. Add detailed comments for vhost_zerocopy_signal_used call 3. Add sleep in vhost shutting down instead of busy-wait for outstanding DMAs. 4. Copy small packets, don't do zero-copy callback in mavtap, mark it's DMA done in vhost 5. change zerocopy to bool in macvtap. It integrates V5 review comments from MST and Michał Mirosław 1. Prevent userspace apps from holding skb userspace buffers by copying userspace buffers to kernel in skb_clone, skb_copy, pskb_copy, pskb_expand_head. 2. It is also used HIGHDMA, SG feature bits to enable ZEROCOPY to remove the dependency of a new feature bit, we can add it later when new feature bit is available. This patchset includes: 1/4: Add a new sock zero-copy flag, SOCK_ZEROCOPY; 2/4: Add a new struct skb_ubuf_info in skb_share_info for userspace buffers release callback when lower device DMA has done for that skb, which is the last reference count gone; Or whenever skb_clone, skb_copy, pskb_copy, pskb_expand_head get call from tcpdump, filtering, these userspace buffers will be copied into kernel ... we don't want userspace apps to hold userspace buffers too long. 3/4: Add vhost zero-copy callback in vhost when skb last refcnt is gone; add vhost_zerocopy_signal_used to notify guest to release TX skb buffers. 4/4: Add macvtap zero-copy in lower device when sending packet is greater than 256 bytes. The patchset is built against most recent net-next linux 2.6.39-rc7. It has passed netperf/netserver multiple streams stress test, tcpdump suspended test, dynamically SG change test. Single TCP_STREAM 120 secs test results over ixgbe 10Gb NIC results: Message BW(Gb/s)qemu-kvm (NumCPU)vhost-net(NumCPU) PerfTop irq/s 4K 7408.57 92.1% 22.6% 1229 4K(Orig)4913.17 118.1% 84.1% 2086 8K 9129.90 89.3% 23.3% 1141 8K(Orig)7094.55 115.9% 84.7% 2157 16K 9178.81 89.1% 23.3% 1139 16K(Orig)8927.1 118.7% 83.4% 2262 64K 9171.43 88.4% 24.9% 1253 64K(Orig)9085.85 115.9% 82.4% 2229 For message size less or equal than 2K, there is a known KVM guest TX overrun issue. With this zero-copy patch, the issue becomes more severe, guest io_exits has tripled than before, so the performance is not good. Once the TX overrun problem has been addressed, I will retest the small message size performance. drivers/net/macvtap.c | 132 ++++++++++++++++++++++++++++++++++++--- drivers/vhost/net.c | 44 +++++++++++++- drivers/vhost/vhost.c | 49 +++++++++++++++ drivers/vhost/vhost.h | 13 ++++ include/linux/netdevice.h | 10 +++ include/linux/skbuff.h | 26 ++++++++ include/net/sock.h | 1 + net/core/skbuff.c | 81 ++++++++++++++++++++++++- 8 files changed, 345 insertions(+), 17 deletions(-) -- 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/