On Tue, Dec 27, 2011 at 10:29:55AM +0900, Simon Horman wrote: > On Mon, Dec 26, 2011 at 03:11:40PM -0500, Jesse Gross wrote: > > On Fri, Dec 16, 2011 at 3:47 AM, Simon Horman <[email protected]> wrote: > > > Hi, > > > > > > I have observed high rates of packet loss when using OVS to "forward" > > > packets to a GRE or VXNET port. This packet loss does not occur to > > > anywhere near the same extent when OVS is used to "forward" packets to > > > a port that does not use tunnelling. > > > > Can you tell specifically where the packets are getting dropped? When > > encapsulating 64-byte packets the tunnel overhead is nearly as large > > as the payload, so that could account for additional stress. > > Hi Jesse, > > Good point with regards to overhead, I had not considered that. > > I haven't isolated where the packet loss is occurring, other > than that the packets are received by the machine running OVS > and their encapsulated version is not transmitted. I'll see > if I can narrow things down.
Hi Jesse, I looked into this a little further and it seems that most if not all the dropped packets are accounted as "dropped" in the qdisc on the outgoing ethernet interface. (perhaps that was obvious?) I tried tweaking the qdisc, removing the default mq qdisc an replacing it with a pfifo with various limits between 1000 and 4096, but this did not seem to have an impact noticeable beyond the noise in there results. I also replotted the results previously posted. Rather than the rate of packet loss I have plotted the packet rate. This shows that there seems to be a limit a little over 600,000packets/s. The outgoing ethernet link is a 10G link (I verified that is the negotiated rate), so 600,000packets/s should not be a problem for the link, even if the packets are expanded to 128 bytes.
rate.pdf
Description: Adobe PDF document
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