Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933313AbaD3J3B (ORCPT ); Wed, 30 Apr 2014 05:29:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36611 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933145AbaD3J2y (ORCPT ); Wed, 30 Apr 2014 05:28:54 -0400 Date: Wed, 30 Apr 2014 13:19:50 +0300 From: "Michael S. Tsirkin" To: "Zhangjie (HZ)" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net, linville@tuxdriver.com, jeffrey.t.kirsher@intel.com, rusty@rustcorp.com.au, jasowang@redhat.com, qinchuanyu@huawei.com, liuyongan@huawei.com, zhaoshenglong@huawei.com Subject: Re: [PATCH net-next] virtio-net: Set needed_headroom for virtio-net when VIRTIO_F_ANY_LAYOUT is true Message-ID: <20140430101950.GA22654@redhat.com> References: <535F824A.5060804@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <535F824A.5060804@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 29, 2014 at 06:43:22PM +0800, Zhangjie (HZ) wrote: > 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 Thanks for your patience! Acked-by: Michael S. Tsirkin > --- > 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; > -- > 1.9.0.msysgit.0 > -- 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/