On Friday 06 May 2016 10:33 PM, Ben Pfaff wrote:
But I'm still having trouble understanding the whole design here.
Without this patch, OVN applies ingress policing to packets received
from (typically) a VM. This limits the rate at which the VM can
introduce packets into the network, and thus acts as a direct (if
primitive) way to limit the VM's bandwidth resource usage on the
machine's physical interface.
With this patch, OVN applies shaping to packets*sent* to (typically) a
VM. This limits the rate at which the VM can consume packets*from* the
network. This has no direct effect on the VM's consumption of bandwidth
resources on the network, because the packets that are discarded have
already consumed RX resources on the machine's physical interface and
there is in fact no direct way to prevent remote machines from sending
packets for the local machine to receive. It might have an indirect
effect on the VM's bandwidth consumption, since remote senders using
(e.g.) TCP will notice that their packets were dropped and reduce their
sending rate, but it's far less efficient at it than shaping packets
going out to the network.
Thank you for the information Ben.
The design I expected to see in OVN, eventually, was this:
- Each VM/VIF gets assigned a queue. Packets received from the
VM are tagged with the queue using an OpenFlow "set_queue"
action (dunno if we have this as an OVN logical action yet but
it's easily added).
- OVN programs the machine's physical interface with a linux-htb
or linux-hfsc qdisc that grants some min-rate to each queue.
From what I understand, to setup egress shaping for a VIF interface
- We need a physical interface attached to br-int
- QOS and Queue tables has to be setup for the port entry that
corresponds to the physical interface
- Packets received from VIF are put in these queues using set_queue.
Is my understanding correct?
Is there any way that HTB/HFSC queues can work without a physical
interface attached to br-int? if not are we going to mandate in some way
that a physical interface has to be attached to br-int?
Thank you,
Babu
Thanks,
Babu
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