[ovs-discuss] queue buffer

[Ben Pfaff]

Please don't drop the mailing list.

The FAQ says:

Q: I configured QoS, correctly, but my measurements show that it isn't
   working as well as I expect.

A: With the Linux kernel, the Open vSwitch implementation of QoS has
   two aspects:

       - Open vSwitch configures a subset of Linux kernel QoS
         features, according to what is in OVSDB.  It is possible that
         this code has bugs.  If you believe that this is so, then you
         can configure the Linux traffic control (QoS) stack directly
         with the "tc" program.  If you get better results that way,
         you can send a detailed bug report to bugs at openvswitch.org.

         It is certain that Open vSwitch cannot configure every Linux
         kernel QoS feature.  If you need some feature that OVS cannot
         configure, then you can also use "tc" directly (or add that
         feature to OVS).

       - The Open vSwitch implementation of OpenFlow allows flows to
         be directed to particular queues.  This is pretty simple and
         unlikely to have serious bugs at this point.

   However, most problems with QoS on Linux are not bugs in Open
   vSwitch at all.  They tend to be either configuration errors
   (please see the earlier questions in this section) or issues with
   the traffic control (QoS) stack in Linux.  The Open vSwitch
   developers are not experts on Linux traffic control.  We suggest
   that, if you believe you are encountering a problem with Linux
   traffic control, that you consult the tc manpages (e.g. tc(8),
   tc-htb(8), tc-hfsc(8)), web resources (e.g. http://lartc.org/), or
   mailing lists (e.g. http://vger.kernel.org/vger-lists.html#netdev).


On Mon, Sep 29, 2014 at 11:19:05PM -0700, shiva rad wrote:
> 
> 
>  well I configured my ovs to create a Qos with 3 queues each with 33Mbit/s max rate, I assigned flows to the queues and tested the queues with iperf and it works fine, but when I generate traffic which exceeds 33Mbit/s I get no loss, and all the traffic passes successfully. I can't understand why this happens? 
> 
> 
> On Tuesday, September 30, 2014 9:16 AM, Ben Pfaff <blp at nicira.com> wrote:
>  
> 
> 
> I don't even know what the question means.
> http://linux.die.net/man/8/tc-htb doesn't talk about a buffer size.
> 
> 
> On Mon, Sep 29, 2014 at 10:43:53PM -0700, shiva rad wrote:
> > 
> > 
> >  
> > what about question A ? I can't find any answers for this one! 
> > 
> > 
> > On Tuesday, September 30, 2014 8:52 AM, Ben Pfaff <blp at nicira.com> wrote:
> >  
> > 
> > 
> > On Mon, Sep 29, 2014 at 10:18:36PM -0700, shiva rad wrote:
> > > I have some questions about creating queues in ovs:
> > > 
> > > A). how we can set buffer size for queues?
> > > 
> > > B)In Ovs we can create a QOS with multiple queues with commands
> > >  below:
> > > 1:ovs-vsctl set port eth1 qos=@newqos \
> > > 2: -- --id=@newqos create qos type=linux-htb \
> > > 3: other-config:max-rate=200000000 queues=0=@q0,1=@q1 \
> > > 4: -- --id=@q0 create queue \
> > > 5: other-config:min-rate=100000000 \
> > > 6: other-config:max-rate=100000000 \
> > > 7: -- --id=@q1 create queue \
> > > 8: other-config:min-rate=50000000 \
> > > 9: other-config:max-rate=50000000
> > > 
> > > What is the difference between max-rate in line 3 for the whole qos and the other max-rate commands in line 6 and 9?
> > > 
> > > C) Does ovs works with other qos types beside linux-htb?
> > 
> > B and C, at least, are answered in the OVS documentation.  Please read
> > 
> > it.