On Fri, Jan 07, 2011 at 10:23:58AM +0900, Simon Horman wrote: > On Thu, Jan 06, 2011 at 05:38:01PM -0500, Jesse Gross wrote: > > [ snip ] > > > > I know that everyone likes a nice netperf result but I agree with > > Michael that this probably isn't the right question to be asking. I > > don't think that socket buffers are a real solution to the flow > > control problem: they happen to provide that functionality but it's > > more of a side effect than anything. It's just that the amount of > > memory consumed by packets in the queue(s) doesn't really have any > > implicit meaning for flow control (think multiple physical adapters, > > all with the same speed instead of a virtual device and a physical > > device with wildly different speeds). The analog in the physical > > world that you're looking for would be Ethernet flow control. > > Obviously, if the question is limiting CPU or memory consumption then > > that's a different story. > > Point taken. I will see if I can control CPU (and thus memory) consumption > using cgroups and/or tc. I have found that I can successfully control the throughput using the following techniques 1) Place a tc egress filter on dummy0 2) Use ovs-ofctl to add a flow that sends skbs to dummy0 and then eth1, this is effectively the same as one of my hacks to the datapath that I mentioned in an earlier mail. The result is that eth1 "paces" the connection. 3) 2) + place a tc egress filter on eth1 Which mostly makes sense to me although I am a little confused about why 1) needs a filter on dummy0 (a filter on eth1 has no effect) but 3) needs a filter on eth1 (a filter on dummy0 has no effect, even if the skb is sent to dummy0 last. I also had some limited success using CPU cgroups, though obviously that targets CPU usage and thus the effect on throughput is fairly course. In short, its a useful technique but not one that bares further discussion here. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
