If "ovs-vswitchd" manages the data paths, why does it have a utility that
lets me create more of them. And when I create them I cannot use them. I am
stuck in a loop :) . 

-----Original Message-----
From: Ben Pfaff [mailto:[email protected]] 
Sent: Thursday, May 3, 2018 4:41 PM
To: [email protected]
Cc: [email protected]
Subject: Re: [ovs-discuss] Multiple dpdk-netdev datapath with OVS 2.9

On Wed, May 02, 2018 at 10:02:04PM +0500, [email protected]
wrote:
> I am trying to create multiple dpdk-netdev based data paths with OVS 
> 2.9 and DPDK 16.11 running on CentOS 7.4. I am able to create multiple 
> data paths using "ovs-appctl dpctl/add-dp netdev@netdev1" and I can 
> see a new data path created with "ovs-appctl dpctl/show". However I 
> cannot add any interfaces (dpdk or otherwise), and I cannot set this 
> data path as datapath_type to any bridge.

That's not useful or a good idea.  ovs-vswitchd manages datapaths itself.
Adding and removing them yourself will not help.

> Just a precap to why I am trying to do this, I am working with a lot 
> of OVS OpenFlow rules (around 0.5 million) matching layer 3 and layer 
> 4 fields. The incoming traffic is more than 40G (4 x10G Intel x520s), 
> and has multiple parallel flows (over a million IPs). With this the 
> OVS performance decreases and each port is forwarding only around 250 
> Mb/s. I am using multiple RX queues (4-6), with single RX queue it 
> drops to 70 Mb/s. Now if I shutdown three 10G interfaces, an 
> interesting thing happen, and OVS starts forwarding over 7Gb/s for 
> that single interface. That got me thinking, maybe the reason for low 
> performance is 40 G traffic hitting a single bridges flow tables, how 
> about creating multiple bridges with multiple flow tables. With this 
> setup the situation remained same, and now the only common thing 
> between the
> 4 interfaces is the data path. They are not sharing anything else. 
> They are polled by dedicated vCPUs, and they are in different tables.
> 
>  
> 
> Can anyone explain this bizarre scenario of why the OVS is able to 
> forward more traffic over single interface polled by 6 vCPUs, compared 
> to 4 interfaces polled by 24 vCPUs.
> 
> Also is there a way to create multiple data paths and remove this 
> dependency also.

You can create multiple bridges with "ovs-vsctl add-br".  OVS doesn't use
multiple datapaths.

Maybe someone who understands the DPDK port better can suggest some reason
for the performance characteristics that you see.

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