On 4/1/2012 2:03 PM, Jon Elson wrote: > Kent A. Reed wrote: >> With a preempt_RT enabled kernel 2.6.33.7.2-rt30 and an appropriately >> modified EMC2.4.4 [patches from Michael Büsch and Jeff Eppler] running >> on an IBM Thinkpad T40 with a 1500MHz PentiumM cpu, the author measured >> the following: >> ----- >> 1) the EMC2 latency-test >> >> Servo Thread: 1ms Max Jitter 261101ns >> Base Thread: 50us Max Jitter 101701ns >> >> > Well, these are ghastly numbers! The 1ms thread has jitter of 26% of > the period, and > the 50us thread has jitter of 204% of the thread period! That will > cause system lockups, > I think. > > Jon > I agree, Jon, but that's the different topic I alluded to at the end of my reply.
Whether preemption is the right approach or a Thinkpad laptop is the appropriate platform or an otherwise unmodified kernel/configuration is acceptable are all questions that I can't resolve without using the right tools to measure their performance. My point was only that this article clearly illustrates the tools differ even when assessing a single system so we have to be very careful comparing results measured using different tools on different systems. As an aside, it was interesting to me that while the author of the bitmuster article made note of the fact that different tools reported different numbers, he/she seemed indifferent to the actual numbers reported. Regards, Kent ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
