From 6ebbc1a6383fe78be3c0961d1475043ac6cc2542 Mon Sep 17 00:00:00 2001 From: "Zhangjie \\(HZ\\)" Date: Tue, 29 Apr 2014 18:43:22 +0800 Subject: [PATCH] virtio-net: Set needed_headroom for virtio-net when VIRTIO_F_ANY_LAYOUT is true 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 | 0.57 | 692232 | 0.61 | 742420 | | 256 | 1.60 | 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 | | 4096 | 6.98 | 637468 | 7.21 | 658471 | +-------+---------+---------+---------+---------+ Signed-off-by: Zhang Jie Acked-by: Rusty Russell Acked-by: Jason Wang Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/virtio_net.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 8a852b5..b852bb3 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; -- 2.7.4