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
