From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [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 16:31:16 +0300 Message-ID: <20140428133116.GA15572@redhat.com> References: <535E5235.4000903@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, jasowang@redhat.com, qinchuanyu@huawei.com, liuyongan@huawei.com To: "Zhangjie (HZ)" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22837 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751716AbaD1OUk (ORCPT ); Mon, 28 Apr 2014 10:20:40 -0400 Content-Disposition: inline In-Reply-To: <535E5235.4000903@huawei.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Apr 28, 2014 at 09:05:57PM +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 | 0.573 | 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 Thanks, results look nice. However - please check Documentation/email-clients.txt and set up your client to send well-formed patches, then pls repost. You also want to Cc all relevant people and lists: use the get_maintainer.pl script to get the list. Also, you need to Cc Dave Miller if you want him to apply your patch. > --- > 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 >