Open Stack

Hi Satish,

Actually, the guess interface is not using tap anymore.

    <interface type='vhostuser'>
      <mac address='fa:16:3e:76:77:dd'/>
      <source type='unix' path='/var/run/openvswitch/vhu3766ee8a-86'
mode='server'/>
      <target dev='vhu3766ee8a-86'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>

It's totally bypass the kernel stack ?




On Fri, Sep 8, 2023 at 5:02 AM Satish Patel <satish.txt at gmail.com> wrote:

> I did test OVS-DPDK and it helps offload the packet process on compute
> nodes, But what about VMs it will still use a tap interface to attach from
> compute to vm and bottleneck will be in vm. I strongly believe that we have
> to run DPDK based guest to pass through the kernel stack.
>
> I love to hear from other people if I am missing something here.
>
> On Thu, Sep 7, 2023 at 5:27 PM Ha Noi <hanoi952022 at gmail.com> wrote:
>
>> Oh. I heard from someone on the reddit said that Ovs-dpdk is transparent
>> with user?
>>
>> So It’s not correct?
>>
>> On Thu, 7 Sep 2023 at 22:13 Satish Patel <satish.txt at gmail.com> wrote:
>>
>>> Because DPDK required DPDK support inside guest VM. It's not
>>> suitable for general purpose workload. You need your guest VM network to
>>> support DPDK to get 100% throughput.
>>>
>>> On Thu, Sep 7, 2023 at 8:06 AM Ha Noi <hanoi952022 at gmail.com> wrote:
>>>
>>>> Hi Satish,
>>>>
>>>> Why dont you use DPDK?
>>>>
>>>> Thanks
>>>>
>>>> On Thu, 7 Sep 2023 at 19:03 Satish Patel <satish.txt at gmail.com> wrote:
>>>>
>>>>> I totally agreed with Sean on all his points but trust me, I have
>>>>> tried everything possible to tune OS, Network stack, multi-queue, NUMA, CPU
>>>>> pinning and name it.. but I didn't get any significant improvement. You may
>>>>> gain 2 to 5% gain with all those tweek. I am running the entire workload on
>>>>> sriov and life is happy except no LACP bonding.
>>>>>
>>>>> I am very interesting is this project
>>>>> https://docs.openvswitch.org/en/latest/intro/install/afxdp/
>>>>>
>>>>> On Thu, Sep 7, 2023 at 6:07 AM Ha Noi <hanoi952022 at gmail.com> wrote:
>>>>>
>>>>>> Dear Smoney,
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Thu, Sep 7, 2023 at 12:41 AM <smooney at redhat.com> wrote:
>>>>>>
>>>>>>> On Wed, 2023-09-06 at 11:43 -0400, Satish Patel wrote:
>>>>>>> > Damn! We have noticed the same issue around 40k to 55k PPS. Trust
>>>>>>> me
>>>>>>> > nothing is wrong in your config. This is just a limitation of the
>>>>>>> software
>>>>>>> > stack and kernel itself.
>>>>>>> its partly determined by your cpu frequency.
>>>>>>> kernel ovs of yesteryear could handel about 1mpps total on a ~4GHZ
>>>>>>> cpu. with per port troughpuyt being lower dependin on what
>>>>>>> qos/firewall
>>>>>>> rules that were apllied.
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> My CPU frequency is 3Ghz and using CPU Intel Gold 2nd generation. I
>>>>>> think the problem is tuning in the compute node inside. But I cannot find
>>>>>> any guide or best practices for it.
>>>>>>
>>>>>>
>>>>>>
>>>>>>> moving form iptables firewall to ovs firewall can help to some degree
>>>>>>> but your partly trading connection setup time for statead state
>>>>>>> troughput
>>>>>>> with the overhead of the connection tracker in ovs.
>>>>>>>
>>>>>>> using stateless security groups can help
>>>>>>>
>>>>>>> we also recently fixed a regression cause by changes in newer
>>>>>>> versions of ovs.
>>>>>>> this was notable in goign form rhel 8 to rhel 9 where litrally it
>>>>>>> reduced
>>>>>>> small packet performce to 1/10th and jumboframes to about 1/2
>>>>>>> on master we have a config option that will set the default qos on a
>>>>>>> port to linux-noop
>>>>>>>
>>>>>>> https://github.com/openstack/os-vif/blob/master/vif_plug_ovs/ovs.py#L106-L125
>>>>>>>
>>>>>>> the backports are propsoed upstream
>>>>>>> https://review.opendev.org/q/Id9ef7074634a0f23d67a4401fa8fca363b51bb43
>>>>>>> and we have backported this downstream to adress that performance
>>>>>>> regression.
>>>>>>> the upstram backport is semi stalled just ebcasue we wanted to
>>>>>>> disucss if we shoudl make ti opt in
>>>>>>> by default upstream while backporting but it might be helpful for
>>>>>>> you if this is related to yoru current
>>>>>>> issues.
>>>>>>>
>>>>>>> 40-55 kpps is kind of low for kernel ovs but if you have a low
>>>>>>> clockrate cpu, hybrid_plug + incorrect qos
>>>>>>> then i could see you hitting such a bottelneck.
>>>>>>>
>>>>>>> one workaround by the way without the os-vif workaround backported
>>>>>>> is to set
>>>>>>> /proc/sys/net/core/default_qdisc to not apply any qos or a low
>>>>>>> overhead qos type
>>>>>>> i.e. sudo sysctl -w net.core.default_qdisc=pfifo_fast
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>> that may or may not help but i would ensure that your are not usign
>>>>>>> somting like fqdel or cake
>>>>>>> for net.core.default_qdisc and if you are try changing it to
>>>>>>> pfifo_fast and see if that helps.
>>>>>>>
>>>>>>> there isnet much you can do about the cpu clock rate but ^ is
>>>>>>> somethign you can try for free
>>>>>>> note it wont actully take effect on an exsitng vm if you jsut change
>>>>>>> the default but you can use
>>>>>>> tc to also chagne the qdisk for testing. hard rebooting the vm
>>>>>>> shoudl also make the default take effect.
>>>>>>>
>>>>>>> the only other advice i can give assuming kernel ovs is the only
>>>>>>> option you have is
>>>>>>>
>>>>>>> to look at
>>>>>>>
>>>>>>> https://docs.openstack.org/nova/latest/configuration/config.html#libvirt.rx_queue_size
>>>>>>>
>>>>>>> https://docs.openstack.org/nova/latest/configuration/config.html#libvirt.tx_queue_size
>>>>>>> and
>>>>>>>
>>>>>>> https://docs.openstack.org/nova/latest/configuration/extra-specs.html#hw:vif_multiqueue_enabled
>>>>>>>
>>>>>>> if the bottelneck is actully in qemu or the guest kernel rather then
>>>>>>> ovs adjusting the rx/tx queue size and
>>>>>>> using multi queue can help. it will have no effect if ovs is the
>>>>>>> bottel neck.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> I have set this option to 1024, and enable multiqueue as well. But it
>>>>>> did not help.
>>>>>>
>>>>>>
>>>>>>> >
>>>>>>> > On Wed, Sep 6, 2023 at 9:21 AM Ha Noi <hanoi952022 at gmail.com>
>>>>>>> wrote:
>>>>>>> >
>>>>>>> > > Hi Satish,
>>>>>>> > >
>>>>>>> > > Actually, our customer get this issue when the tx/rx above only
>>>>>>> 40k pps.
>>>>>>> > > So what is the threshold of this throughput for OvS?
>>>>>>> > >
>>>>>>> > >
>>>>>>> > > Thanks and regards
>>>>>>> > >
>>>>>>> > > On Wed, 6 Sep 2023 at 20:19 Satish Patel <satish.txt at gmail.com>
>>>>>>> wrote:
>>>>>>> > >
>>>>>>> > > > Hi,
>>>>>>> > > >
>>>>>>> > > > This is normal because OVS or LinuxBridge wire up VMs using
>>>>>>> TAP interface
>>>>>>> > > > which runs on kernel space and that drives higher interrupt
>>>>>>> and that makes
>>>>>>> > > > the kernel so busy working on handling packets. Standard
>>>>>>> OVS/LinuxBridge
>>>>>>> > > > are not meant for higher PPS.
>>>>>>> > > >
>>>>>>> > > > If you want to handle higher PPS then look for DPDK or SRIOV
>>>>>>> deployment.
>>>>>>> > > > ( We are running everything in SRIOV because of high PPS
>>>>>>> requirement)
>>>>>>> > > >
>>>>>>> > > > On Tue, Sep 5, 2023 at 11:11 AM Ha Noi <hanoi952022 at gmail.com>
>>>>>>> wrote:
>>>>>>> > > >
>>>>>>> > > > > Hi everyone,
>>>>>>> > > > >
>>>>>>> > > > > I'm using Openstack Train and Openvswitch for ML2 driver and
>>>>>>> GRE for
>>>>>>> > > > > tunnel type. I tested our network performance between two
>>>>>>> VMs and suffer
>>>>>>> > > > > packet loss as below.
>>>>>>> > > > >
>>>>>>> > > > > VM1: IP: 10.20.1.206
>>>>>>> > > > >
>>>>>>> > > > > VM2: IP: 10.20.1.154 <https://10.20.1.154/24>
>>>>>>> > > > >
>>>>>>> > > > > VM3: IP: 10.20.1.72
>>>>>>> > > > >
>>>>>>> > > > >
>>>>>>> > > > > Using iperf3 to testing performance between VM1 and VM2.
>>>>>>> > > > >
>>>>>>> > > > > Run iperf3 client and server on both VMs.
>>>>>>> > > > >
>>>>>>> > > > > On VM2: iperf3 -t 10000 -b 130M -l 442 -P 6 -u -c 10.20.1.206
>>>>>>> > > > >
>>>>>>> > > > > On VM1: iperf3 -t 10000 -b 130M -l 442 -P 6 -u -c 10.20.1.154
>>>>>>> > > > > <https://10.20.1.154/24>
>>>>>>> > > > >
>>>>>>> > > > >
>>>>>>> > > > > Using VM3 ping into VM1, then the packet is lost and the
>>>>>>> latency is
>>>>>>> > > > > quite high.
>>>>>>> > > > >
>>>>>>> > > > >
>>>>>>> > > > > ping -i 0.1 10.20.1.206
>>>>>>> > > > >
>>>>>>> > > > > PING 10.20.1.206 (10.20.1.206) 56(84) bytes of data.
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=1 ttl=64 time=7.70 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=2 ttl=64 time=6.90 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=3 ttl=64 time=7.71 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=4 ttl=64 time=7.98 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=6 ttl=64 time=8.58 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=7 ttl=64 time=8.34 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=8 ttl=64 time=8.09 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=10 ttl=64 time=4.57 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=11 ttl=64 time=8.74 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=12 ttl=64 time=9.37 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=14 ttl=64 time=9.59 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=15 ttl=64 time=7.97 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=16 ttl=64 time=8.72 ms
>>>>>>> > > > >
>>>>>>> > > > > 64 bytes from 10.20.1.206: icmp_seq=17 ttl=64 time=9.23 ms
>>>>>>> > > > >
>>>>>>> > > > > ^C
>>>>>>> > > > >
>>>>>>> > > > > --- 10.20.1.206 ping statistics ---
>>>>>>> > > > >
>>>>>>> > > > > 34 packets transmitted, 28 received, 17.6471% packet loss,
>>>>>>> time 3328ms
>>>>>>> > > > >
>>>>>>> > > > > rtt min/avg/max/mdev = 1.396/6.266/9.590/2.805 ms
>>>>>>> > > > >
>>>>>>> > > > >
>>>>>>> > > > >
>>>>>>> > > > > Does any one get this issue ?
>>>>>>> > > > >
>>>>>>> > > > > Please help me. Thanks
>>>>>>> > > > >
>>>>>>> > > >
>>>>>>>
>>>>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.openstack.org/pipermail/openstack-discuss/attachments/20230908/643d43e3/attachment-0001.htm>