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Re: [Qemu-devel] wiki: update missing info on "Enabling multi-queue" sec


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] wiki: update missing info on "Enabling multi-queue" section of vhost-user
Date: Thu, 24 Mar 2016 11:31:31 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

On 03/21/2016 12:10 PM, Lin Ma wrote:
Hi Marcel,
I found that the information on "Enabling multi-queue" in 
http://wiki.qemu.org/Features/vhost-user-ovs-dpdk
are inaccurate.
In ovs 2.5 or older, The option 'other_config:n-dpdk-rxqs' is used and there is 
no options:n_rxq.
The n_rxq is available since post 2.5.0.
But when setup an interface's option using ovs-vsctl, It doesn't check whether 
the option is valid or not.
So if a user follows the instruction of above wiki page to setup the vhost-user 
multi queues in ovs 2.5-,
The user wont get any error information but the vms which have vhost-user multi 
queues nics dont work and the user
gets confused.
I think that we should mentioned on wiki:
In ovs 2.5 or older version: The usage is:
......
ovs-vsctl set Open_vSwitch . other_config:n-dpdk-rxqs=<queues_nr, the same as 
QEMU>
//BTW: It only supports setting up same number of rx queues for all of PMD 
netdevs.
......
In post ovs 2.5, The usage is:
......
ovs-vsctl set Interface vhost-user1 options:n_rxq=<queues_nr, the same as QEMU>
ovs-vsctl set Interface vhost-user2 options:n_rxq=<queues_nr, the same as QEMU>
......
Moreover, For vhost-user live migration support, Because qemu needs vhost-user 
backend providing
VHOST_USER_PROTOCOL_F_LOG_SHMFD feature bit since commit 1be0ac2.
The dpdk commit d639996 provides this feature bit but it isn't available in 
dpdk 2.2.0, It may be merged into 2.3.0.
In this case, If a user uses qemu 2.5+dpdk 2.2+ovs, The vhost-user live 
migration wont succeed.
Should it be mentioned on wiki as well? I dont have permissions to update wiki 
pages, So sending the information to list.
Lin

Hi Lin,

Thank you for the important update, would you want update the wiki yourself?
If you have the time, please reply me on a private thread with the desired 
username
and I'll supply a temporary password.

Thanks,
Marcel




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