Please don't drop the list. I think that you need to just investigate further, profile, timestamp/log different pieces of the processing. One direction might be to monitor when the actual OpenFlow requests/responses are sent between OVS and POX. I don't think that either OVS or POX are made for this kind of use case, so I don't have any more information than you about where the latency is introduced.
On 20 April 2016 at 11:28, Adil Ahmad <adilahma...@gmail.com> wrote: > Hi, > > Thanks for the reply. Yes, I understand the points that you've made. So, > currently I am able to fetch updated stats about every ~1.5 ms usually, > after changing the line. But after about every 30ms, I experience a 'jump', > which means that the flow stats event callback returns after about ~50 ms. I > think hardware constraints come into play but I am not sure. Can you help > explain this? > > Adil > > On Wed, Apr 20, 2016 at 11:16 PM, Joe Stringer <j...@ovn.org> wrote: >> >> On 19 April 2016 at 12:56, Adil Ahmad <adilahma...@gmail.com> wrote: >> > Hi, >> > >> > I am trying to decrease the time that OVS takes to update its >> > packet/byte >> > counters. I was previously told that the line 898 of >> > ofproto-dpif-upcall.c >> > which is part of function udpif_validator is used to set the timer. The >> > line >> > is as follows: >> > >> > // Original >> > poll_timer_wait_until(start_time + MIN(ofproto_max_idle, 500)); >> > >> > //Changed >> > poll_timer_wait_until(start_time + MIN(ofproto_max_idle, 1)); >> >> Note that this timer simply sets the typical time that the revalidator >> thread will sleep *after finishing all of its work*, so it doesn't >> guarantee that stats will be synchronized every 1ms. >> >> > I changed it to 1 and I can now get updated counters at ~1ms frequency. >> > However, I have noticed that after about 30 ms, there is a sudden jump >> > and >> > the stats handler takes a jump by about ~50ms. My controller is POX >> > based >> > and my timer is python datetime timer with microsecond granularity. >> > >> > Can anyone tell me why I see the jump? >> >> What do you mean by "jump"? >> >> All you've done is increase the consistency of stats within OVS - the >> kernel module is more closely synchronised with the OpenFlow rules in >> userspace. If you're fetching the stats via OpenFlow, then the main >> thread might not be able to wake up and provide stats as quickly as >> you want. Even if that is possible, there's still a whole host of >> other potential pitfalls to trying to get realtime stats. > > _______________________________________________ discuss mailing list discuss@openvswitch.org http://openvswitch.org/mailman/listinfo/discuss
