On Sun, Nov 06, 2011 at 09:56:10PM -0800, Jesse Gross wrote: > On Fri, Nov 4, 2011 at 4:43 PM, Ben Pfaff <b...@nicira.com> wrote: > > NetFlow active timeouts were only mixed in with flow expiration for > > convenience: both processes need to iterate all the facets. ??But > > an upcoming commit will change flow expiration to work in terms of > > a new "subfacet" entity, so they will no longer fit together well. > > > > This change could be seen as an optimization, since NetFlow active > > timeouts don't ordinarily have to run as often as flow expiration, > > especially when the flow expiration rate is stepped up due to a > > large volume of flows. > > This has a pretty significant effect on the accuracy of the timeouts > that I'm not sure is intended. Currently, active timeouts are done on > a per-flow basis starting from time of first use. However, this > essentially starts a per-bridge timer on first configuration that must > first expire in order to check the per-flow timer. So with the > default timeout of 10 minutes, the first active timeout will occur > somewhere between 10 and 20 minutes after first use. This only > happens for the first one though since they will tend to synchronize. > However, I think that there is a potential for the two timers to > desynchronize, resulting in apparently random doubling of intervals. > For example, netflow_run() is also called from gen_netflow_rec() when > it fills up a packet but does not check the return code, skipping the > active timeout if a timer tick occurred in that window. Finally, the > current active timeout code distributes reporting over a large span of > time but this concentrates all of them at once, which could cause a > load spike in the collector if a number of switches are brought up at > the same time.
Hmm. Maybe I should just do NetFlow reporting once a second (as it was before). What do you think? Thanks, Ben. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
