[ovs-dev] [PATCH] FAQ: Add QoS section.
jpettit at nicira.com
Tue Jan 22 18:17:16 UTC 2013
Looks good. Thanks!
On Jan 22, 2013, at 10:15 AM, Ben Pfaff <blp at nicira.com> wrote:
> On Tue, Jan 22, 2013 at 10:06:12AM -0800, Justin Pettit wrote:
>> I hope you had this section queued up for review, and not that you
>> whipped it up in the minute since you responded to that QoS question
>> on ovs-discuss. I already feel inadequate enough.
> It took me about half an hour to write it this morning. I hope that it
> will save me more than half an hour in 2013.
>>> +A: Suppose that you want to set up bridge br0 connected to physical
>>> + Ethernet port eth0 (a 1 Gbps device) and virtual machine interface
> Thanks, fixed.
>>> + vif1.0 and vif2.0, and that you want to limit traffic from vif1.0
>>> + to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you
>>> + could configure the bridge this way:
>>> + ovs-vsctl -- \
>>> + add-br br0 -- \
>>> + add-port br0 eth0 -- \
>>> + add-port br0 vif1.0 -- set interface vif1.0 ofport_request=1 -- \
>>> + add-port br0 vif2.0 -- set interface vif2.0 ofport_request=2 -- \
>> I haven't run the commands either, but I think these ports you
>> requested may have been given to br0 and eth0 already, since we try to
>> allocate from 1. (If you update these ones, there are a couple of
>> places later on that also reference these OpenFlow port numbers.)
> I would think that explicit requests should take precedence over
> defaults, but I think the actual implementation may be weak in that
> I changed them to 5 and 6. (I'm trying to use numbers that are not
> close to 1.0 or 2.0 (or 10 or 20) to keep readers from thinking that the
> actual numbers are significant.)
> Here's a revised version, still not tested.
> --8<--------------------------cut here-------------------------->8--
> From: Ben Pfaff <blp at nicira.com>
> Date: Tue, 22 Jan 2013 10:14:13 -0800
> Subject: [PATCH] FAQ: Add QoS section.
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> FAQ | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 104 insertions(+)
> diff --git a/FAQ b/FAQ
> index ab1c1cc..ab4338e 100644
> --- a/FAQ
> +++ b/FAQ
> @@ -455,6 +455,110 @@ A: In version 1.9.0, OVS switched to using a single datapath that is
> commands provide similar functionality that is scoped by the bridge.
> +Quality of Service (QoS)
> +Q: How do I configure Quality of Service (QoS)?
> +A: Suppose that you want to set up bridge br0 connected to physical
> + Ethernet port eth0 (a 1 Gbps device) and virtual machine interfaces
> + vif1.0 and vif2.0, and that you want to limit traffic from vif1.0
> + to eth0 to 10 Mbps and from vif2.0 to eth0 to 20 Mbps. Then, you
> + could configure the bridge this way:
> + ovs-vsctl -- \
> + add-br br0 -- \
> + add-port br0 eth0 -- \
> + add-port br0 vif1.0 -- set interface vif1.0 ofport_request=5 -- \
> + add-port br0 vif2.0 -- set interface vif2.0 ofport_request=6 -- \
> + set port eth0 qos=@newqos -- \
> + --id=@newqos create qos type=linus-htb \
> + other-config:max-rate=1000000000 \
> + queues:123=@vif10queue \
> + queues:234=@vif20queue -- \
> + --id=@vif10queue create queue other-config:max-rate=10000000 -- \
> + --id=@vif20queue create queue other-config:max-rate=20000000
> + At this point, bridge br0 is configured with the ports and eth0 is
> + configured with the queues that you need for QoS, but nothing is
> + actually directing packets from vif1.0 or vif2.0 to the queues that
> + we have set up for them. That means that all of the packets to
> + eth0 are going to the "default queue", which is not what we want.
> + We use OpenFlow to direct packets from vif1.0 and vif2.0 to the
> + queues reserved for them:
> + ovs-ofctl add-flow br0 in_port=5,actions=set_queue:123,normal
> + ovs-ofctl add-flow br0 in_port=6,actions=set_queue:234,normal
> + Each of the above flows matches on the input port, sets up the
> + appropriate queue (123 for vif1.0, 234 for vif2.0), and then
> + executes the "normal" action, which performs the same switching
> + that Open vSwitch would have done without any OpenFlow flows being
> + present. (We know that vif1.0 and vif2.0 have OpenFlow port
> + numbers 5 and 6, respectively, because we set their ofport_request
> + columns above. If we had not done that, then we would have needed
> + to find out their port numbers before setting up these flows.)
> + Now traffic going from vif1.0 or vif2.0 to eth0 should be
> + rate-limited.
> + By the way, if you delete the bridge created by the above commands,
> + with:
> + ovs-vsctl del-br br0
> + then that will leave one unreferenced QoS record and two
> + unreferenced Queue records in the Open vSwich database. One way to
> + clear them out, assuming you don't have other QoS or Queue records
> + that you want to keep, is:
> + ovs-vsctl -- --all destroy QoS -- --all destroy Queue
> +Q: I configured Quality of Service (QoS) in my OpenFlow network by
> + adding records to the QoS and Queue table, but the results aren't
> + what I expect.
> +A: Did you install OpenFlow flows that use your queues? This is the
> + primary way to tell Open vSwitch which queues you want to use. If
> + you don't do this, then the default queue will be used, which will
> + probably not have the effect you want.
> + Refer to the previous question for an example.
> +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).
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