[Qemu-devel] GRO not happening in VM with VxLAN

[Qemu-devel] GRO not happening in VM with VxLAN

[Santosh R]

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All,

   I am testing VxLAN performance in VM. For this I am using below command
to bring up the VM.
# qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &

This is resulting in lower throughput in VM. On looking further I found
that GRO is not happing on the tap interface.
Using tcpdump I could see GRO happeing in physcial nic, vxlan and bridge
interface. but _not_ on tap interface.

So, I thought to use veth pair instead of the tap interface in VM. What is
the command to do this?
Also,
1. Why is rx-checksumming off for tap interface?
2. Why is GRO not happening with tap interface?

Pls copy me in all the replies as I am not on the list.

# brctl show
bridge name     bridge id               STP enabled     interfaces
br-vx           8000.323a9146b2d2       no              tap0
                                                        vxlan0
# ethtool -k eth35
Features for eth35:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: on
        tx-checksum-ip-generic: off [fixed]
        tx-checksum-ipv6: on
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: off [fixed]
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp6-segmentation: on
udp-fragmentation-offload: off [fixed]
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: on
tx-vlan-offload: on
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-ipip-segmentation: off [fixed]
tx-sit-segmentation: off [fixed]
tx-udp_tnl-segmentation: on
tx-mpls-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
busy-poll: on [fixed]

# ethtool -k vxlan0
Features for vxlan0:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: off [fixed]
        tx-checksum-ip-generic: on
        tx-checksum-ipv6: off [fixed]
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: off [fixed]
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp6-segmentation: on
udp-fragmentation-offload: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: on
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: off [fixed]
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: on [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-ipip-segmentation: off [fixed]
tx-sit-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-mpls-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: on
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
busy-poll: off [fixed]

# ethtool -k tap0
Features for tap0:
rx-checksumming: off [fixed]
tx-checksumming: on
        tx-checksum-ipv4: off [fixed]
        tx-checksum-ip-generic: on
        tx-checksum-ipv6: off [fixed]
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: off [fixed]
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: on
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp6-segmentation: on
udp-fragmentation-offload: off [fixed]
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: on
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: off [fixed]
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-ipip-segmentation: off [fixed]
tx-sit-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-mpls-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: on
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
busy-poll: off [fixed]
Thanks
-Santosh

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Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Vlad Yasevich]

On 06/29/2015 01:46 AM, Santosh R wrote:
> All,
> 
>    I am testing VxLAN performance in VM. For this I am using below command
> to bring up the VM.
> # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
> virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
> tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
> 
> This is resulting in lower throughput in VM. On looking further I found
> that GRO is not happing on the tap interface.
> Using tcpdump I could see GRO happeing in physcial nic, vxlan and bridge
> interface. but _not_ on tap interface.

I don't think this is GRO.  GRO  only happens at the lowest possible layer.
For packets coming from external sources, that happens just above the nic
when the packet enters the host for the first time.  From then on, the features
of other devices determine if the large aggregated packet will be segmented
again or not.


> 
> So, I thought to use veth pair instead of the tap interface in VM. What is
> the command to do this?

veth pair will not help with this.  you need a tap or a macvtap to have
VM  talk to host.

> Also,
> 1. Why is rx-checksumming off for tap interface?

because tap doesn't do checksum validation.  it allows lower level devices or
VM to do so.

> 2. Why is GRO not happening with tap interface?
> 

Again.  I don't think it's GRO.  Try capturing traffic at tap and see if you get
large packets (more the 1 mtu long) on the tap.  If not, then someone else is fragmenting
packets and you need to find who.

-vlad

> Pls copy me in all the replies as I am not on the list.
> 
> # brctl show
> bridge name     bridge id               STP enabled     interfaces
> br-vx           8000.323a9146b2d2       no              tap0
>                                                         vxlan0
> # ethtool -k eth35
> Features for eth35:
> rx-checksumming: on
> tx-checksumming: on
>         tx-checksum-ipv4: on
>         tx-checksum-ip-generic: off [fixed]
>         tx-checksum-ipv6: on
>         tx-checksum-fcoe-crc: off [fixed]
>         tx-checksum-sctp: off [fixed]
> scatter-gather: on
>         tx-scatter-gather: on
>         tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
>         tx-tcp-segmentation: on
>         tx-tcp-ecn-segmentation: on
>         tx-tcp6-segmentation: on
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
> generic-receive-offload: on
> large-receive-offload: off [fixed]
> rx-vlan-offload: on
> tx-vlan-offload: on
> ntuple-filters: off [fixed]
> receive-hashing: off [fixed]
> highdma: on
> rx-vlan-filter: off [fixed]
> vlan-challenged: off [fixed]
> tx-lockless: off [fixed]
> netns-local: off [fixed]
> tx-gso-robust: off [fixed]
> tx-fcoe-segmentation: off [fixed]
> tx-gre-segmentation: off [fixed]
> tx-ipip-segmentation: off [fixed]
> tx-sit-segmentation: off [fixed]
> tx-udp_tnl-segmentation: on
> tx-mpls-segmentation: off [fixed]
> fcoe-mtu: off [fixed]
> tx-nocache-copy: off
> loopback: off [fixed]
> rx-fcs: off [fixed]
> rx-all: off [fixed]
> tx-vlan-stag-hw-insert: off [fixed]
> rx-vlan-stag-hw-parse: off [fixed]
> rx-vlan-stag-filter: off [fixed]
> l2-fwd-offload: off [fixed]
> busy-poll: on [fixed]
> 
> # ethtool -k vxlan0
> Features for vxlan0:
> rx-checksumming: on
> tx-checksumming: on
>         tx-checksum-ipv4: off [fixed]
>         tx-checksum-ip-generic: on
>         tx-checksum-ipv6: off [fixed]
>         tx-checksum-fcoe-crc: off [fixed]
>         tx-checksum-sctp: off [fixed]
> scatter-gather: on
>         tx-scatter-gather: on
>         tx-scatter-gather-fraglist: off [fixed]
> tcp-segmentation-offload: on
>         tx-tcp-segmentation: on
>         tx-tcp-ecn-segmentation: on
>         tx-tcp6-segmentation: on
> udp-fragmentation-offload: on
> generic-segmentation-offload: on
> generic-receive-offload: on
> large-receive-offload: off [fixed]
> rx-vlan-offload: off [fixed]
> tx-vlan-offload: on
> ntuple-filters: off [fixed]
> receive-hashing: off [fixed]
> highdma: off [fixed]
> rx-vlan-filter: off [fixed]
> vlan-challenged: off [fixed]
> tx-lockless: on [fixed]
> netns-local: off [fixed]
> tx-gso-robust: off [fixed]
> tx-fcoe-segmentation: off [fixed]
> tx-gre-segmentation: off [fixed]
> tx-ipip-segmentation: off [fixed]
> tx-sit-segmentation: off [fixed]
> tx-udp_tnl-segmentation: off [fixed]
> tx-mpls-segmentation: off [fixed]
> fcoe-mtu: off [fixed]
> tx-nocache-copy: off
> loopback: off [fixed]
> rx-fcs: off [fixed]
> rx-all: off [fixed]
> tx-vlan-stag-hw-insert: on
> rx-vlan-stag-hw-parse: off [fixed]
> rx-vlan-stag-filter: off [fixed]
> l2-fwd-offload: off [fixed]
> busy-poll: off [fixed]
> 
> # ethtool -k tap0
> Features for tap0:
> rx-checksumming: off [fixed]
> tx-checksumming: on
>         tx-checksum-ipv4: off [fixed]
>         tx-checksum-ip-generic: on
>         tx-checksum-ipv6: off [fixed]
>         tx-checksum-fcoe-crc: off [fixed]
>         tx-checksum-sctp: off [fixed]
> scatter-gather: on
>         tx-scatter-gather: on
>         tx-scatter-gather-fraglist: on
> tcp-segmentation-offload: on
>         tx-tcp-segmentation: on
>         tx-tcp-ecn-segmentation: on
>         tx-tcp6-segmentation: on
> udp-fragmentation-offload: off [fixed]
> generic-segmentation-offload: on
> generic-receive-offload: on
> large-receive-offload: off [fixed]
> rx-vlan-offload: off [fixed]
> tx-vlan-offload: on
> ntuple-filters: off [fixed]
> receive-hashing: off [fixed]
> highdma: off [fixed]
> rx-vlan-filter: off [fixed]
> vlan-challenged: off [fixed]
> tx-lockless: off [fixed]
> netns-local: off [fixed]
> tx-gso-robust: off [fixed]
> tx-fcoe-segmentation: off [fixed]
> tx-gre-segmentation: off [fixed]
> tx-ipip-segmentation: off [fixed]
> tx-sit-segmentation: off [fixed]
> tx-udp_tnl-segmentation: off [fixed]
> tx-mpls-segmentation: off [fixed]
> fcoe-mtu: off [fixed]
> tx-nocache-copy: off
> loopback: off [fixed]
> rx-fcs: off [fixed]
> rx-all: off [fixed]
> tx-vlan-stag-hw-insert: on
> rx-vlan-stag-hw-parse: off [fixed]
> rx-vlan-stag-filter: off [fixed]
> l2-fwd-offload: off [fixed]
> busy-poll: off [fixed]
> Thanks
> -Santosh
> 

Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Santosh R]

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On Mon, Jun 29, 2015 at 9:04 PM, Vlad Yasevich <vyasevic@redhat.com> wrote:

> On 06/29/2015 01:46 AM, Santosh R wrote:
> > All,
> >
> >    I am testing VxLAN performance in VM. For this I am using below
> command
> > to bring up the VM.
> > # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
> > virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
> > tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
> >
> > This is resulting in lower throughput in VM. On looking further I found
> > that GRO is not happing on the tap interface.
> > Using tcpdump I could see GRO happeing in physcial nic, vxlan and bridge
> > interface. but _not_ on tap interface.
>
> I don't think this is GRO.  GRO  only happens at the lowest possible layer.
> For packets coming from external sources, that happens just above the nic
> when the packet enters the host for the first time.  From then on, the
> features
> of other devices determine if the large aggregated packet will be segmented
> again or not.
>
>
> >
> > So, I thought to use veth pair instead of the tap interface in VM. What
> is
> > the command to do this?
>
> veth pair will not help with this.  you need a tap or a macvtap to have
> VM  talk to host.
>
> > Also,
> > 1. Why is rx-checksumming off for tap interface?
>
> because tap doesn't do checksum validation.  it allows lower level devices
> or
> VM to do so.
>
> > 2. Why is GRO not happening with tap interface?
> >
>
> Again.  I don't think it's GRO.  Try capturing traffic at tap and see if
> you get
> large packets (more the 1 mtu long) on the tap.  If not, then someone else
> is fragmenting
> packets and you need to find who.
>
[Santosh]:  Thanks for the reply.
With VxLAN, aggregated packets are seen on physical, VxLAN and bridge
interface but _not_ on the tap interface.
Without VxLAN, I do see aggregated (GRO) packets all the way upto VM (i.e.
physical, bridge and tap interface).
As you rightly pointed, looks like VxLAN packets are getting fragmented.
Any pointers to look for?


>
> -vlad
>
> > Pls copy me in all the replies as I am not on the list.
> >
> > # brctl show
> > bridge name     bridge id               STP enabled     interfaces
> > br-vx           8000.323a9146b2d2       no              tap0
> >                                                         vxlan0
> > # ethtool -k eth35
> > Features for eth35:
> > rx-checksumming: on
> > tx-checksumming: on
> >         tx-checksum-ipv4: on
> >         tx-checksum-ip-generic: off [fixed]
> >         tx-checksum-ipv6: on
> >         tx-checksum-fcoe-crc: off [fixed]
> >         tx-checksum-sctp: off [fixed]
> > scatter-gather: on
> >         tx-scatter-gather: on
> >         tx-scatter-gather-fraglist: off [fixed]
> > tcp-segmentation-offload: on
> >         tx-tcp-segmentation: on
> >         tx-tcp-ecn-segmentation: on
> >         tx-tcp6-segmentation: on
> > udp-fragmentation-offload: off [fixed]
> > generic-segmentation-offload: on
> > generic-receive-offload: on
> > large-receive-offload: off [fixed]
> > rx-vlan-offload: on
> > tx-vlan-offload: on
> > ntuple-filters: off [fixed]
> > receive-hashing: off [fixed]
> > highdma: on
> > rx-vlan-filter: off [fixed]
> > vlan-challenged: off [fixed]
> > tx-lockless: off [fixed]
> > netns-local: off [fixed]
> > tx-gso-robust: off [fixed]
> > tx-fcoe-segmentation: off [fixed]
> > tx-gre-segmentation: off [fixed]
> > tx-ipip-segmentation: off [fixed]
> > tx-sit-segmentation: off [fixed]
> > tx-udp_tnl-segmentation: on
> > tx-mpls-segmentation: off [fixed]
> > fcoe-mtu: off [fixed]
> > tx-nocache-copy: off
> > loopback: off [fixed]
> > rx-fcs: off [fixed]
> > rx-all: off [fixed]
> > tx-vlan-stag-hw-insert: off [fixed]
> > rx-vlan-stag-hw-parse: off [fixed]
> > rx-vlan-stag-filter: off [fixed]
> > l2-fwd-offload: off [fixed]
> > busy-poll: on [fixed]
> >
> > # ethtool -k vxlan0
> > Features for vxlan0:
> > rx-checksumming: on
> > tx-checksumming: on
> >         tx-checksum-ipv4: off [fixed]
> >         tx-checksum-ip-generic: on
> >         tx-checksum-ipv6: off [fixed]
> >         tx-checksum-fcoe-crc: off [fixed]
> >         tx-checksum-sctp: off [fixed]
> > scatter-gather: on
> >         tx-scatter-gather: on
> >         tx-scatter-gather-fraglist: off [fixed]
> > tcp-segmentation-offload: on
> >         tx-tcp-segmentation: on
> >         tx-tcp-ecn-segmentation: on
> >         tx-tcp6-segmentation: on
> > udp-fragmentation-offload: on
> > generic-segmentation-offload: on
> > generic-receive-offload: on
> > large-receive-offload: off [fixed]
> > rx-vlan-offload: off [fixed]
> > tx-vlan-offload: on
> > ntuple-filters: off [fixed]
> > receive-hashing: off [fixed]
> > highdma: off [fixed]
> > rx-vlan-filter: off [fixed]
> > vlan-challenged: off [fixed]
> > tx-lockless: on [fixed]
> > netns-local: off [fixed]
> > tx-gso-robust: off [fixed]
> > tx-fcoe-segmentation: off [fixed]
> > tx-gre-segmentation: off [fixed]
> > tx-ipip-segmentation: off [fixed]
> > tx-sit-segmentation: off [fixed]
> > tx-udp_tnl-segmentation: off [fixed]
> > tx-mpls-segmentation: off [fixed]
> > fcoe-mtu: off [fixed]
> > tx-nocache-copy: off
> > loopback: off [fixed]
> > rx-fcs: off [fixed]
> > rx-all: off [fixed]
> > tx-vlan-stag-hw-insert: on
> > rx-vlan-stag-hw-parse: off [fixed]
> > rx-vlan-stag-filter: off [fixed]
> > l2-fwd-offload: off [fixed]
> > busy-poll: off [fixed]
> >
> > # ethtool -k tap0
> > Features for tap0:
> > rx-checksumming: off [fixed]
> > tx-checksumming: on
> >         tx-checksum-ipv4: off [fixed]
> >         tx-checksum-ip-generic: on
> >         tx-checksum-ipv6: off [fixed]
> >         tx-checksum-fcoe-crc: off [fixed]
> >         tx-checksum-sctp: off [fixed]
> > scatter-gather: on
> >         tx-scatter-gather: on
> >         tx-scatter-gather-fraglist: on
> > tcp-segmentation-offload: on
> >         tx-tcp-segmentation: on
> >         tx-tcp-ecn-segmentation: on
> >         tx-tcp6-segmentation: on
> > udp-fragmentation-offload: off [fixed]
> > generic-segmentation-offload: on
> > generic-receive-offload: on
> > large-receive-offload: off [fixed]
> > rx-vlan-offload: off [fixed]
> > tx-vlan-offload: on
> > ntuple-filters: off [fixed]
> > receive-hashing: off [fixed]
> > highdma: off [fixed]
> > rx-vlan-filter: off [fixed]
> > vlan-challenged: off [fixed]
> > tx-lockless: off [fixed]
> > netns-local: off [fixed]
> > tx-gso-robust: off [fixed]
> > tx-fcoe-segmentation: off [fixed]
> > tx-gre-segmentation: off [fixed]
> > tx-ipip-segmentation: off [fixed]
> > tx-sit-segmentation: off [fixed]
> > tx-udp_tnl-segmentation: off [fixed]
> > tx-mpls-segmentation: off [fixed]
> > fcoe-mtu: off [fixed]
> > tx-nocache-copy: off
> > loopback: off [fixed]
> > rx-fcs: off [fixed]
> > rx-all: off [fixed]
> > tx-vlan-stag-hw-insert: on
> > rx-vlan-stag-hw-parse: off [fixed]
> > rx-vlan-stag-filter: off [fixed]
> > l2-fwd-offload: off [fixed]
> > busy-poll: off [fixed]
> > Thanks
> > -Santosh
> >
>
>

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Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Santosh R]

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On Mon, Jun 29, 2015 at 9:24 PM, Santosh R <skrastapur@gmail.com> wrote:

>
> On Mon, Jun 29, 2015 at 9:04 PM, Vlad Yasevich <vyasevic@redhat.com>
> wrote:
>
>> On 06/29/2015 01:46 AM, Santosh R wrote:
>> > All,
>> >
>> >    I am testing VxLAN performance in VM. For this I am using below
>> command
>> > to bring up the VM.
>> > # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
>> > virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
>> > tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
>> >
>> > This is resulting in lower throughput in VM. On looking further I found
>> > that GRO is not happing on the tap interface.
>> > Using tcpdump I could see GRO happeing in physcial nic, vxlan and bridge
>> > interface. but _not_ on tap interface.
>>
>> I don't think this is GRO.  GRO  only happens at the lowest possible
>> layer.
>> For packets coming from external sources, that happens just above the nic
>> when the packet enters the host for the first time.  From then on, the
>> features
>> of other devices determine if the large aggregated packet will be
>> segmented
>> again or not.
>>
>>
>> >
>> > So, I thought to use veth pair instead of the tap interface in VM. What
>> is
>> > the command to do this?
>>
>> veth pair will not help with this.  you need a tap or a macvtap to have
>> VM  talk to host.
>>
>> > Also,
>> > 1. Why is rx-checksumming off for tap interface?
>>
>> because tap doesn't do checksum validation.  it allows lower level
>> devices or
>> VM to do so.
>>
>> > 2. Why is GRO not happening with tap interface?
>> >
>>
>> Again.  I don't think it's GRO.  Try capturing traffic at tap and see if
>> you get
>> large packets (more the 1 mtu long) on the tap.  If not, then someone
>> else is fragmenting
>> packets and you need to find who.
>>
> [Santosh]:  Thanks for the reply.
> With VxLAN, aggregated packets are seen on physical, VxLAN and bridge
> interface but _not_ on the tap interface.
> Without VxLAN, I do see aggregated (GRO) packets all the way upto VM (i.e.
> physical, bridge and tap interface).
> As you rightly pointed, looks like VxLAN packets are getting fragmented.
> Any pointers to look for?
>
>
By the way, I was referring below link for VxLAN testing and ran into the
GRO issue.
This mentions "The veth0 is suppose to be connected to the VM, while the
veth1 is connected to the Linux bridge".
https://community.mellanox.com/docs/DOC-1473

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Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Santosh R]

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Since the vxlan UDP header checksum is 0, udp_tunnel_gro_complete (called
via vxlan_gro_complete) is setting SKB_GSO_UDP_TUNNEL in
skb_shinfo(skb)->gso_type.
Later when bridge interface tries to forward this packet to tap interface
(br_dev_queue_push_xmit -> __dev_queue_xmit -> validate_xmit_skb)
netif_needs_gso will succeed (skb_gso_ok returns 0)
resulting in packet segmentation (which was earlier aggregated) as tap
interface doesn't have this feature. Is there a way to enable
tx-udp_tnl-segmentation for tap interface?

# ethtool -K tap0 tx-udp_tnl-segmentation on
Could not change any device features

# ethtool -k tap0 | grep -i tnl
tx-udp_tnl-segmentation: off [fixed]

On Tue, Jun 30, 2015 at 12:24 PM, Santosh R <skrastapur@gmail.com> wrote:

>
> On Mon, Jun 29, 2015 at 9:24 PM, Santosh R <skrastapur@gmail.com> wrote:
>
>>
>> On Mon, Jun 29, 2015 at 9:04 PM, Vlad Yasevich <vyasevic@redhat.com>
>> wrote:
>>
>>> On 06/29/2015 01:46 AM, Santosh R wrote:
>>> > All,
>>> >
>>> >    I am testing VxLAN performance in VM. For this I am using below
>>> command
>>> > to bring up the VM.
>>> > # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
>>> > virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
>>> > tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
>>> >
>>> > This is resulting in lower throughput in VM. On looking further I found
>>> > that GRO is not happing on the tap interface.
>>> > Using tcpdump I could see GRO happeing in physcial nic, vxlan and
>>> bridge
>>> > interface. but _not_ on tap interface.
>>>
>>> I don't think this is GRO.  GRO  only happens at the lowest possible
>>> layer.
>>> For packets coming from external sources, that happens just above the nic
>>> when the packet enters the host for the first time.  From then on, the
>>> features
>>> of other devices determine if the large aggregated packet will be
>>> segmented
>>> again or not.
>>>
>>>
>>> >
>>> > So, I thought to use veth pair instead of the tap interface in VM.
>>> What is
>>> > the command to do this?
>>>
>>> veth pair will not help with this.  you need a tap or a macvtap to have
>>> VM  talk to host.
>>>
>>> > Also,
>>> > 1. Why is rx-checksumming off for tap interface?
>>>
>>> because tap doesn't do checksum validation.  it allows lower level
>>> devices or
>>> VM to do so.
>>>
>>> > 2. Why is GRO not happening with tap interface?
>>> >
>>>
>>> Again.  I don't think it's GRO.  Try capturing traffic at tap and see if
>>> you get
>>> large packets (more the 1 mtu long) on the tap.  If not, then someone
>>> else is fragmenting
>>> packets and you need to find who.
>>>
>> [Santosh]:  Thanks for the reply.
>> With VxLAN, aggregated packets are seen on physical, VxLAN and bridge
>> interface but _not_ on the tap interface.
>> Without VxLAN, I do see aggregated (GRO) packets all the way upto VM
>> (i.e. physical, bridge and tap interface).
>> As you rightly pointed, looks like VxLAN packets are getting fragmented.
>> Any pointers to look for?
>>
>>
> By the way, I was referring below link for VxLAN testing and ran into the
> GRO issue.
> This mentions "The veth0 is suppose to be connected to the VM, while the
> veth1 is connected to the Linux bridge".
> https://community.mellanox.com/docs/DOC-1473
>

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Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Vlad Yasevich]

On 07/01/2015 02:50 PM, Santosh R wrote:
> Since the vxlan UDP header checksum is 0, udp_tunnel_gro_complete (called
> via vxlan_gro_complete) is setting SKB_GSO_UDP_TUNNEL in
> skb_shinfo(skb)->gso_type.
> Later when bridge interface tries to forward this packet to tap interface
> (br_dev_queue_push_xmit -> __dev_queue_xmit -> validate_xmit_skb)
> netif_needs_gso will succeed (skb_gso_ok returns 0)
> resulting in packet segmentation (which was earlier aggregated) as tap
> interface doesn't have this feature. Is there a way to enable
> tx-udp_tnl-segmentation for tap interface?

No.  Those features are set by qemu when the guest is created and
mirror any features that are supported by the guest.  So, if the guest
virtio doesn't have that feature, neither will the tap device.

Which kernel version are you using on the host?

-vlad

> 
> # ethtool -K tap0 tx-udp_tnl-segmentation on
> Could not change any device features
> 
> # ethtool -k tap0 | grep -i tnl
> tx-udp_tnl-segmentation: off [fixed]
> 
> On Tue, Jun 30, 2015 at 12:24 PM, Santosh R <skrastapur@gmail.com> wrote:
> 
>>
>> On Mon, Jun 29, 2015 at 9:24 PM, Santosh R <skrastapur@gmail.com> wrote:
>>
>>>
>>> On Mon, Jun 29, 2015 at 9:04 PM, Vlad Yasevich <vyasevic@redhat.com>
>>> wrote:
>>>
>>>> On 06/29/2015 01:46 AM, Santosh R wrote:
>>>>> All,
>>>>>
>>>>>    I am testing VxLAN performance in VM. For this I am using below
>>>> command
>>>>> to bring up the VM.
>>>>> # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
>>>>> virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
>>>>> tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
>>>>>
>>>>> This is resulting in lower throughput in VM. On looking further I found
>>>>> that GRO is not happing on the tap interface.
>>>>> Using tcpdump I could see GRO happeing in physcial nic, vxlan and
>>>> bridge
>>>>> interface. but _not_ on tap interface.
>>>>
>>>> I don't think this is GRO.  GRO  only happens at the lowest possible
>>>> layer.
>>>> For packets coming from external sources, that happens just above the nic
>>>> when the packet enters the host for the first time.  From then on, the
>>>> features
>>>> of other devices determine if the large aggregated packet will be
>>>> segmented
>>>> again or not.
>>>>
>>>>
>>>>>
>>>>> So, I thought to use veth pair instead of the tap interface in VM.
>>>> What is
>>>>> the command to do this?
>>>>
>>>> veth pair will not help with this.  you need a tap or a macvtap to have
>>>> VM  talk to host.
>>>>
>>>>> Also,
>>>>> 1. Why is rx-checksumming off for tap interface?
>>>>
>>>> because tap doesn't do checksum validation.  it allows lower level
>>>> devices or
>>>> VM to do so.
>>>>
>>>>> 2. Why is GRO not happening with tap interface?
>>>>>
>>>>
>>>> Again.  I don't think it's GRO.  Try capturing traffic at tap and see if
>>>> you get
>>>> large packets (more the 1 mtu long) on the tap.  If not, then someone
>>>> else is fragmenting
>>>> packets and you need to find who.
>>>>
>>> [Santosh]:  Thanks for the reply.
>>> With VxLAN, aggregated packets are seen on physical, VxLAN and bridge
>>> interface but _not_ on the tap interface.
>>> Without VxLAN, I do see aggregated (GRO) packets all the way upto VM
>>> (i.e. physical, bridge and tap interface).
>>> As you rightly pointed, looks like VxLAN packets are getting fragmented.
>>> Any pointers to look for?
>>>
>>>
>> By the way, I was referring below link for VxLAN testing and ran into the
>> GRO issue.
>> This mentions "The veth0 is suppose to be connected to the VM, while the
>> veth1 is connected to the Linux bridge".
>> https://community.mellanox.com/docs/DOC-1473
>>
> 

Re: [Qemu-devel] [Qemu-discuss] GRO not happening in VM with VxLAN

[Santosh R]

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I am using 3.18 kernel.

#uname -a
Linux Indra.asicdesigners.com 3.18.0 #11 SMP Wed Jul 1 21:49:44 IST 2015
x86_64 x86_64 x86_64 GNU/Linux
#cat /etc/issue
Red Hat Enterprise Linux Server release 6.5 (Santiago)
Kernel \r on an \m

As mentioned in my initial post, this is how I am starting the VM. How do
we enable/pass tx-udp_tnl-segmentation feature in the below command? Is
this an option while creating the VM?
*# qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
tap,id=tap0,script=no,vhost=on -drive file=/root/vdisk_rhel65.img &*

On Thu, Jul 2, 2015 at 12:37 AM, Vlad Yasevich <vyasevic@redhat.com> wrote:

> On 07/01/2015 02:50 PM, Santosh R wrote:
> > Since the vxlan UDP header checksum is 0, udp_tunnel_gro_complete (called
> > via vxlan_gro_complete) is setting SKB_GSO_UDP_TUNNEL in
> > skb_shinfo(skb)->gso_type.
> > Later when bridge interface tries to forward this packet to tap interface
> > (br_dev_queue_push_xmit -> __dev_queue_xmit -> validate_xmit_skb)
> > netif_needs_gso will succeed (skb_gso_ok returns 0)
> > resulting in packet segmentation (which was earlier aggregated) as tap
> > interface doesn't have this feature. Is there a way to enable
> > tx-udp_tnl-segmentation for tap interface?
>
> No.  Those features are set by qemu when the guest is created and
> mirror any features that are supported by the guest.  So, if the guest
> virtio doesn't have that feature, neither will the tap device.
>
> Which kernel version are you using on the host?
>
> -vlad
>
> >
> > # ethtool -K tap0 tx-udp_tnl-segmentation on
> > Could not change any device features
> >
> > # ethtool -k tap0 | grep -i tnl
> > tx-udp_tnl-segmentation: off [fixed]
> >
> > On Tue, Jun 30, 2015 at 12:24 PM, Santosh R <skrastapur@gmail.com>
> wrote:
> >
> >>
> >> On Mon, Jun 29, 2015 at 9:24 PM, Santosh R <skrastapur@gmail.com>
> wrote:
> >>
> >>>
> >>> On Mon, Jun 29, 2015 at 9:04 PM, Vlad Yasevich <vyasevic@redhat.com>
> >>> wrote:
> >>>
> >>>> On 06/29/2015 01:46 AM, Santosh R wrote:
> >>>>> All,
> >>>>>
> >>>>>    I am testing VxLAN performance in VM. For this I am using below
> >>>> command
> >>>>> to bring up the VM.
> >>>>> # qemu-system-x86_64 -m 4096 -smp 4 -boot c -device
> >>>>> virtio-net-pci,netdev=tap0,mac=00:11:22:33:44:55 -netdev
> >>>>> tap,id=tap0,script=no,vhost=on  -drive file=/root/vdisk_rhel65.img &
> >>>>>
> >>>>> This is resulting in lower throughput in VM. On looking further I
> found
> >>>>> that GRO is not happing on the tap interface.
> >>>>> Using tcpdump I could see GRO happeing in physcial nic, vxlan and
> >>>> bridge
> >>>>> interface. but _not_ on tap interface.
> >>>>
> >>>> I don't think this is GRO.  GRO  only happens at the lowest possible
> >>>> layer.
> >>>> For packets coming from external sources, that happens just above the
> nic
> >>>> when the packet enters the host for the first time.  From then on, the
> >>>> features
> >>>> of other devices determine if the large aggregated packet will be
> >>>> segmented
> >>>> again or not.
> >>>>
> >>>>
> >>>>>
> >>>>> So, I thought to use veth pair instead of the tap interface in VM.
> >>>> What is
> >>>>> the command to do this?
> >>>>
> >>>> veth pair will not help with this.  you need a tap or a macvtap to
> have
> >>>> VM  talk to host.
> >>>>
> >>>>> Also,
> >>>>> 1. Why is rx-checksumming off for tap interface?
> >>>>
> >>>> because tap doesn't do checksum validation.  it allows lower level
> >>>> devices or
> >>>> VM to do so.
> >>>>
> >>>>> 2. Why is GRO not happening with tap interface?
> >>>>>
> >>>>
> >>>> Again.  I don't think it's GRO.  Try capturing traffic at tap and see
> if
> >>>> you get
> >>>> large packets (more the 1 mtu long) on the tap.  If not, then someone
> >>>> else is fragmenting
> >>>> packets and you need to find who.
> >>>>
> >>> [Santosh]:  Thanks for the reply.
> >>> With VxLAN, aggregated packets are seen on physical, VxLAN and bridge
> >>> interface but _not_ on the tap interface.
> >>> Without VxLAN, I do see aggregated (GRO) packets all the way upto VM
> >>> (i.e. physical, bridge and tap interface).
> >>> As you rightly pointed, looks like VxLAN packets are getting
> fragmented.
> >>> Any pointers to look for?
> >>>
> >>>
> >> By the way, I was referring below link for VxLAN testing and ran into
> the
> >> GRO issue.
> >> This mentions "The veth0 is suppose to be connected to the VM, while the
> >> veth1 is connected to the Linux bridge".
> >> https://community.mellanox.com/docs/DOC-1473
> >>
> >
>
>

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