I don't know how to explain it.
On Thu, Jan 16, 2014 at 03:32:33PM -0600, Xiaoye Sun wrote: > Hi Han and Ben, > > I changed the FLOW_MISS_MAX_BATCH value to to 1 but the problem still > exists. I do see that upcalls are handle individually in userspace. but the > RTT of the higher rate are still less than the RTT of the lower rate... > Does the ovs kernel use a similar batching mechanism? > > > On Thu, Jan 16, 2014 at 1:24 PM, Xiaoye Sun <[email protected]> wrote: > > > @ Han, I guess FLOW_MISS_MAX_BATCH should be the right place to change. > > For my understanding, ovs userspace will batch all the packets it received > > and the put packets from same flow into a "group", one group for each flow. > > So I guess there are two levels of "batching". > > > > > > > > > > On Thu, Jan 16, 2014 at 12:17 PM, Zhou, Han <[email protected]> wrote: > > > >> Hi Xiaoye, > >> > >> > Is there any way to disable this batching mechanism in the ovs kernel > >> so that each upcall only contains one packet? > >> Batching is a mechanism of the user space upcall handler rather than OVS > >> kernel. > >> To disable it you can change below macro in ofproto/ofproto-dpif-upcall.h: > >> #define FLOW_MISS_MAX_BATCH 50 => 1 > >> > >> However, I wonder how would batching affect your RTT result. > >> On Wed, Jan 15, 2014 at 5:11 PM, Ben Pfaff <[email protected]> wrote: > >> > As the rate > >> > increases, I guess that a batch contains more than one packet, and > >> > it's likely that the batches mix up SYNs and SYN-ACKs, possibly > >> > reducing the latency. > >> > >> @Ben, even if the batches mix up SYNs and SYN-ACKs, they are from > >> different > >> Flows. For SYN and SYN-ACK pairs of each single flow, they can never be > >> mixed in the same batch, because SYN-ACK is not sent out until SYN is > >> delivered > >> to the receiver. So in my opinion, batching can improve the whole > >> throughput but > >> cannot explain the better STT. Did I miss anything here? > >> > >> @Xiaoye, maybe you can change FLOW_MISS_MAX_BATCH to different numbers to > >> verify. > >> > >> Best regards, > >> Han > >> _______________________________________________ > >> discuss mailing list > >> [email protected] > >> http://openvswitch.org/mailman/listinfo/discuss > >> > >> > > > > > > -- > > Xiaoye (Steven) Sun, Ph.D. Student > > Department of Electrical and Computer Engineering (ECE) & Department of > > Computer Science (CS) > > George R. Brown School of Engineering > > Rice University, Houston, Texas, USA > > > > > > -- > Xiaoye (Steven) Sun, Ph.D. Student > Department of Electrical and Computer Engineering (ECE) & Department of > Computer Science (CS) > George R. Brown School of Engineering > Rice University, Houston, Texas, USA _______________________________________________ discuss mailing list [email protected] http://openvswitch.org/mailman/listinfo/discuss
