[ovs-discuss] configuration of min_rate of a queue in OVS

Ben Pfaff blp at ovn.org
Thu Jul 11 21:28:39 UTC 2019


On Tue, Jul 09, 2019 at 12:22:17PM +0200, Miguel Gonzalez wrote:
> Hello all,
> I would like to ask you two questions regarding the configuration of queues
> in an OVS
> 
> 1- I want to define 2 queues with priorities in a port, the queue with the
> higher priority should have all the available BW when is transmitting, and
> the other one should use the remaining BW if its some free.
> In order to do that, I am configuring a HTB with max_rate=100000 and 2
> queues with different priorities:
> sudo ovs-vsctl create queue other-config:priority=2
> other-config:min-rate=10 other-config:burst=80000
> 
> sudo ovs-vsctl create queue other-config:priority=1
> other-config:min-rate=100000 other-config:burst=80000
> 
> sudo ovs-vsctl create qos type=linux-htb \
> other-config:max-rate=100000 \
> queues:2=ac434c08-e58a-43b2-90cb-f490baf948e9 \
> queues:1=45afeab6-75d9-4c5b-a1bb-1aabdf786cce
> 
> The problem is that the min_rate of queue 2 is always 12kbps, even i
> created with 1 bps. Do you know why is that happening? is it the mininmun
> min_rate of an OVS?  How can set the min_rate value to 0?

For QoS, OVS just passes along the configuration to the Linux queuing
discipline implementation, in this case to the linux-htb code.  The
linux-htb code might not be able to accurately implement a 1 bps or 0
bps min_rate.  It's not an OVS limitation, in other words, it's a
limitation in the underlying Linux qdisc.

I'd think that 12 kbps would be pretty close to 0 bps, for a port that
runs at megabits or gigabits.

100000 bps == 100 kbps is a pretty low min-rate for your high-priority
queue, isn't it?

> 2- My second question is also related to the configuration of a queue in a
> port. Moreover, I have a SW with 2 interfaces, and I want to configure one
> queue in one interface that is the incoming and outgoing interface for some
> flows. My problem is that the packets go to the queue, but then they are
> not proccessed.
> Can you also help me here?
> the rule I am creating is the next one:
> sudo ovs-ofctl add-flow -O OpenFlow13 s1
> in_port=1,dl_type=0x0800,nw_tos=0xc0,actions=set_queue:1,in_port

This looks OK, so you might want to check the queue statistics with
"tc".


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