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Hi Satish,



Did your packet loss happen always or it only happened when heavy load?

AFAIK, if you do not tun anything, the vm tap can process about 50kpps before the tap device start to drop packets. 



If it happened in heavy load, couple of things you can try:

1) increase tap queue length, usually the default value is 500, you can try larger. (seems like you already tried)

2) Try to use virtio multi queues feature , see [1]. Virtio use one queue for rx/tx in vm, with this feature you can get more queues. You can check 

3) In rock version, you can use [2] to increase virtio queue size, the default queues size is 256/512, you may increase it to 1024, this would help to increase pps of the tap device.



If all these things can not get your network performance requirement, you may need to move to use dpdk / sriov stuff to get more vm performance.

I did not actually used them in our env, you may refer to [3]



[1] https://specs.openstack.org/openstack/nova-specs/specs/liberty/implemented/libvirt-virtiomq.html

[2] https://specs.openstack.org/openstack/nova-specs/specs/rocky/implemented/libvirt-virtio-set-queue-sizes.html

[3] https://docs.openstack.org/ocata/networking-guide/config-sriov.html



Regards,

Liping Mao



在 2018/9/16 13:07，“Satish Patel”<satish.txt at gmail.com> 写入:



    [root at compute-33 ~]# ifconfig tap5af7f525-5f | grep -i drop

            RX errors 0 dropped 0 overruns 0 frame 0

            TX errors 0 dropped 2528788837 overruns 0 carrier 0 collisions 0

    

    Noticed tap interface dropping TX packets and even after increasing

    txqueue from 1000 to 10000 nothing changed, still getting packet

    drops.

    

    On Sat, Sep 15, 2018 at 4:22 PM Satish Patel <satish.txt at gmail.com> wrote:

    >

    > Folks,

    >

    > I need some advice or suggestion to find out what is going on with my

    > network, we have notice high packet loss on openstack instance and not

    > sure what is going on, same time if i check on host machine and it has

    > zero packet loss.. this is what i did for test...

    >

    > ping 8.8.8.8

    >

    > from instance: 50% packet loss

    > from compute host: 0% packet loss

    >

    > I have disabled TSO/GSO/SG setting on physical compute node but still

    > getting packet loss.

    >

    > We have 10G NIC on our network, look like something related to tap

    > interface setting..

    

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