On Wed, 2015-11-04 at 18:29 +0100, Richard Cochran wrote: > On Wed, Nov 04, 2015 at 01:46:52PM +0000, Shlomi Tubul wrote: > > > For some reason, I see spikes at clients, which are > > unreasonable. Most of the time the offset is around +- 200ns, > > but from time to time it jumps to more than 20 micro second. > > You shouldn't have such spikes. >
Indeed, spikes like this are unexpected. > > Looking at the code of ptp4l, I see that there are filters for > > the delay but not for the offset. > > That is because they are not needed. Offset should be stable, while delay actually can jitter about for various reasons. > > > I updated the code a little it in my environment, just to see > > if the offset is real. For every offset greater than 1 > > microsecond, I updated it to 0. This caused the client to > > synchronize better and not trying to adjust huge offsets. > > You made a band aid, and this papers over the problem. Why not find > out the cause of those spikes? > > > Both server and client are running Intel I210, RH 7.1, linux > > ptp 1.6. > > I have used the i210 quite a lot, and I have never seen such spikes. > > Do you have a direct point to point connection? If not, probably the > equipment in between is to blame. Yes likely the equipment between is an issue if there is any. > > > The setup is running also other applications (Hadoop etc), so > > I am not sure how much it affects. > > The time stamps are taken in hardware at the MAC level, and so > applications should have no effect. > I do not believe that latency affects the actual timestamping equipment in hardware. It could delay the overall timestamp return process, but that doesn't actually add any latency to the timestamp itself since it was already captured, only in how long it takes to return it. Note that the i210 can only timestamp one Tx packet at a time, but the outcome you are seeing is not dropped Tx timestamps, but just spikes in the value? Regards, Jake > Thanks, > Richard > > --------------------------------------------------------------------- > --------- > _______________________________________________ > Linuxptp-devel mailing list > Linuxptp-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linuxptp-devel ------------------------------------------------------------------------------ _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
