On Fri, 2010-02-26 at 10:51 +0800, David V. Cloud wrote: > Hi, > > I read some kernel source. My basic understanding is that, in > net/8021q/vlan_dev.c, vlan_dev_init, the dev->features of vconfig > created interface is defined to be > dev->features |= real_dev->features & real_dev->vlan_features; > > However, in drivers/net/virtio_net.c, vlan_features are never set (I > will assume it would be 0). So, dev->features will be 0 for the > ethX.vid interface. > > I verify it using ethtool -k on each KVM. > # ethtool -k eth0 > shows that rx/tx csum, sg, tso, gso are on > # ethtool -k eth0.3003 > all offloading features are off. > > I think that is why TSO is never enabled when running large package > traffic between two vlan interfaces of different KVMs. > > I also took a look at VMware's pv implementation, which is > drivers/net/vmxnet3/vmxnet3_drv.c, they have enable dev->vlan_features > when probing, by > netdev->vlan_features = netdev->features; > > > I was wondering why vlan_features was not defined in virtio_net. Is it > a BUG? Or, it is due to some constraints? > Could any explain that? I saw the same issue some time back and submitted a couple of patches to address it, but were not accepted as the fix is not done at the right place. Not sure if we can do this right without updating virtio_net_hdr with vlan specific info. http://thread.gmane.org/gmane.linux.network/150197/focus=150838 http://thread.gmane.org/gmane.linux.network/150198/focus=150837 Thanks Sridhar > > Thanks, > -D > > > > On Thu, Feb 25, 2010 at 6:30 PM, David V. Cloud <david.v.cloud@xxxxxxxxx> wrote: > > Hi all, > > I have been deploying two KVMs on my Debian testing box. Two KVMs each > > use one tap device connecting to the host. > > > > When I > > doing netperf with large package size from KVM2 (tap1) to KVM1 (tap0) > > using ethX on them, I could verify that TSO did happened by > > # tcpdump -nt -i tap1 > > I can see messages like, > > IP 192.168.101.2.39994 > 192.168.101.1.41316: Flags [P.], seq > > 7912865:7918657, ack 0, win 92, options [nop,nop,TS val 874151 ecr > > 874803], length 5792 > > > > So, according the 'length', skb didn't get segmented. > > > > However, When I > > (1) setup VLAN using vconfig on KVM2, KVM1, and got two new interface > > eth1.3003, eth0.3003 on both machines. > > (2) netperf between two new interface, TSO no longer showed up, > > # tcpdump -nt -i tap1 > > I only got, > > vlan 3003, p 0, IP 10.214.10.2.42324 > 10.214.10.1.56460: Flags [P.], > > seq 2127976:2129424, ack 1, win 92, options [nop,nop,TS val 926034 ecr > > 926686], length 1448 > > > > So, all the large packages get segmented in virtio (is that right?) > > > > My KVM command line options are, > > kvm -hda $IMG -m 768 -net nic,model=virtio,macaddr=52:54:00:12:34:56 > > -net tap,ifname=$TAP,script=no > > > > > > > > My question is whether it is the expected behavior? Can VLAN tagging > > coexist with TSO in virtio_net driver? > > If this is not desired result. Any hint for fixing the problem? > > > > Thanks > > -D > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
