On Monday 09 February 2009, EBo wrote: > There are some interesting patterns in the actual results. I was > watching not only the ovr_max, but also the lat_max. For me the lat_max > will bounce around between a say -200ns to maybe 300ns, and then jump to > 2000ns to 4000ns blocks, and then sometimes settle back to near 0.
A result (from the RTAI latency test) of 2-4uSec is quite good depending on actual load - What you need to watch for is spikes in the millisecond range indicating a possible SMI issue. > > My own theory (and it is only a theory) about why the cpu hog works is > > related to cache. The hog uses very little memory, and since it keeps > > one CPU busy, that CPU never runs any other code. So the RT code > > doesn't get flushed out of cache, and doesn't have to get fetched back > > into cache later. Running a minimal script that just burns CPU cycles is of little value - An analogy would be to jack up the wheels of a car and run the engine to the red line and claim it will do 150MPH. > The cache theory (which makes seance) would explain the jumping blocks seen > above, but it does not explain my current problem with the non RT side of > the latency test stalling the way it does. If you want to see the effects of cache misses, run a "cache calibrator" - One that has been recommended in the past is http://monetdb.cwi.nl/Calibrator/ > Maybe what is needed is another latency test which uses a > continuous/periodic interrupt. What you _should_ be doing is providing some real-world loads over an extended period, i.e: Start the RTAI latency test then: dd if=/dev/urandom of=/dev/null ping -f -s 1600 -l 1000 localhost # also flood-ping from another box. cd <kernel-src>/ && make -j For more extreme testing, run cpuburn or `:(){ :|:& };:` [1] - Starting up X while the latency-test is running will also give the system a good short term loading, and if it doesn't lock up starting/stopping X, then you will have a solid setup. With X running, any graphics intensive processes will also provide a good workout - Try some of the OpenGL screensavers. [1] :(){ :|:& };: is otherwise known as a fork bomb - Do not try this at home. ------------------------------------------------------------------------------ Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
