From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Zhangjie (HZ)" Subject: [PATCH net-next] virtio-net: Set dev->needed_headroom for virtio-net device when it has the feature VIRTIO_F_ANY_LAYOUT Date: Mon, 28 Apr 2014 21:05:57 +0800 Message-ID: <535E5235.4000903@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: , , , To: Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:34598 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755346AbaD1NGP (ORCPT ); Mon, 28 Apr 2014 09:06:15 -0400 Sender: netdev-owner@vger.kernel.org List-ID: This is a small supplement for commit e7428e95a06fb516fac1308bd0e176e27c0b9287("virtio-net: put virtio-net header inline with data"). TCP packages have enough room to put virtio-net header in, but UDP packages do not. By setting dev->needed_headroom for virtio-net device, UDP packages could have enough room. For UDP packages, sk_buff is alloced in fun __ip_append_data. The size is "alloclen + hh_len + 15", and "hh_len = LL_RESERVED_SPACE(rt->dst.dev);". The Macro is defined as follows: #define LL_RESERVED_SPACE(dev) \ ((((dev)->hard_header_len+(dev)->needed_headroom)\ &~(HH_DATA_MOD - 1)) + HH_DATA_MOD) By default, for UDP packages, after skb is allocated, only 16 bytes reserved. And 2 bytes remained after mac header is set. That is not enough to put virtio-net header in. If we set dev->needed_headroom to 12 or 10 (according to mergeable_rx_bufs is on or off ), more room can be reserved. Then there is enough room for UDP packages to put the header in. test result list as below: guest and host: suse11sp3, netperf, intel 2.4GHz +-------+---------+---------+---------+---------+ | | old | | new | | +-------+---------+---------+---------+---------+ | UDP | Gbit/s | PPs | Gbit/s | PPs | | 64 | 0.573 | 692232 | 0.614 | 742420 | | 256 | 1.6 | 686860 | 1.71 | 733331 | | 512 | 2.92 | 674576 | 3.07 | 710446 | | 1024 | 4.99 | 598977 | 5.17 | 620821 | | 1460 | 5.68 | 483757 | 7.16 | 610519 | +-------+---------+---------+---------+---------+ Signed-off-by: ZhangJie --- drivers/net/virtio_net.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 8a852b5..e18acc3 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1724,6 +1724,13 @@ static int virtnet_probe(struct virtio_device *vdev) if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) vi->has_cvq = true; + if (vi->any_header_sg) { + if (vi->mergeable_rx_bufs) + dev->needed_headroom = sizeof(struct virtio_net_hdr_mrg_rxbuf); + else + dev->needed_headroom = sizeof(struct virtio_net_hdr); + } + /* Use single tx/rx queue pair as default */ vi->curr_queue_pairs = 1; vi->max_queue_pairs = max_queue_pairs; -- 1.7.1