On Dec 6 2012 2:04 PM, Kent A. Reed wrote: > On 12/6/2012 3:38 PM, EBo wrote: >> On Dec 6 2012 12:27 PM, Anders Wallin wrote: >>>> Is the ±20us always happening during the startup? If so, we can >>>> probably work around this. If it is periodic, or happens much >>>> later, >>>> then it points to a real issue. >>>> >>> On my machine the few events at +/- 20us do not occur immediately >>> on >>> startup, but rather randomly after a short while. >>> For these initial tests I was recording about 100k jitter values, >>> so >>> for a >>> 1ms thread it means I ran the logger for about 100 seconds. >> OK. I would say it is real then, and not a startup issue. Good to >> know... >> >> EBo -- > > Be careful not to generalize too much. My somewhat limited experience > is > that every combination of > (motherboard)+(bios)+(cpu)+(specific-rt-mechanism) is capable of > exhibiting qualitatively different behavior. Whether it actually does > is, to me, a matter of test, not conjecture. That's why I've tried to > set up and test a number of different combinations as time permits. > > Several times you and others have talked about connecting the outlier > events to other goings-on by comparing time-stamps with system logs. > Has > anyone actually tried an experiment to do that?
First I guess I will explain that the one assumption that my previous comment made is that if the event happens every once and awhile after the latency tester starts up that it cannot be the startup sequence of the tester itself. That is what I was commenting about. As for the testing the timestamps to sys-logs, that only works if you have stack tracing (or some such) and/or are doing course things like (if I plug something into the USB around 5 seconds into the program running, do I see it come up on the syslogs and any blips in the latency tester? Beyond that I have not had a need to provide such software instrumentation. That of course was ad-hoc testing. What I think we are talking about here is establishing some tools to either automate it, or at least start making a more principled approach. So, yes I agree we need to be careful making more generalizations. Oh yea, in the very distant past I have sat in front of an oscilloscope and looking for blips while I muck with the hardware. But that again was rather ad-hoc. EBo -- ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
