This one perturbs the output ordering just enough to fail two of the sflow unit tests. Sorry I didn't notice that before. I'll post another patch for that.
Neil ------ Neil McKee InMon Corp. http://www.inmon.com On Fri, Sep 2, 2016 at 11:47 AM, Ben Pfaff <b...@ovn.org> wrote: > On Mon, Aug 29, 2016 at 03:32:41PM -0700, Neil McKee wrote: >> This patch changes the order of the steps that are followed >> every second in the sFlow agent. By moving the receiver_tick() >> step to the end, we ensure that any counters that were polled >> during the poller_tick() step are flushed immediately to the >> sFlow collector. This eliminates what was a variable time-delay >> between counters being polled and being flushed. >> >> The variable time-delay that this eliminates could be up to >> a second because counters lingering in the output buffer could be >> flushed at any time by the arrival of random packet-samples. >> >> Since the sFlow standard does not require that a poll-timestamp be sent >> along with the counters the collector must use his receive-time as the >> timestamp, so that extra second of variable delay was "stretching or >> shrinking" the time between successive counter readings. This >> affected any counter-rate calculation that was based only on the delta >> between sucessive samples. The effect was small with a polling >> interval of 60 seconds: just +/- 2%. But the effect grew larger >> when faster polling was configured. For example, if the counters >> were pushed every 5 seconds then the instantaneous rate >> calculations could wander by +/- 20%. For a thorough analysis >> of this problem, see Rick Jones' paper: >> >> "High Frequency sFlow v5 Counter Sampling" >> ftp://ftp.netperf.org/papers/high_freq_sflow/hf_sflow_counters.pdf >> >> So this patch makes it possible to obtain usable results even >> when high-frequency polling is configured. >> >> Signed-off-by: Neil McKee <neil.mc...@inmon.com> > > Thanks, applied to master and branch-2.6. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
