When performance testing the client JRE we do two things which seem to help:
1) check out both the latest and your older / baseline releases of your code. Test them *both*. This lets you plot how you have improved, regardless of what computer your tests are running on. It's also the only way to test things which might vary from computer to computer. 2) always run each test a bunch of times, throw away the first result, then average the rest. This gives you a more consistent result. Throwing away the first one lets you ignore the places where HotSpot hadn't kicked in, or you were thrashing in JVM startup. - Josh On Sep 15, 2009, at 12:45 AM, Fabrizio Giudici wrote: > > Working with imaging, I came to the conclusion that I need continuous > performance testing more than one year ago > (http://netbeans.dzone.com/news/stopwatches-anyone-or-about-co). Of > course, the idea is not mine, but seems surprisingly "old" (2003, > http://www.devx.com/Java/Article/16755). As you can read in my > article, > my continuous performance testing had initially been manual, 1.5 years > ago I developed a few trivial code to at least automatically collect > the > results (then they were manually inserted into an Excel sheet). Since > Hudson allows to plot arbitrary data, the next step I'm going to > complete is to provide those data to Hudson. Due to the very nature of > my functions, I'm not going to strictly assert that a task is > completed > in a certain time, but I'd be satisfied to plot the trend over time, > so > I can see the impact of performance optimizations, and above all I can > make sure that the performance isn't slowly but inexorably getting > worse > refactoring after refactoring. > > Since the time of my article, I got one more problem. My testing > machine, to compute and compare timings against, so far has been my > laptop. The amount of tests is increasing and it has become impossible > to run everything on my laptop each time (otherwise I couldn't use it > for hours), so I've moved the tests to a Hudson slave (a good > 8-processor, where I'm going to exploit the parallelism to compute > multiple tests at the same time). At this point there's the problem: > scheduling parallel tasks is an excellent way to screw up measurements > (while with my laptop I made sure that everything was executed > serially > and there were no other processes consuming CPU in the background). > While at least for some tasks I could strictly measure the CPU time > (by > means of JMX), parts of the tests are related to I/O (loading and > decoding files) - clearly performing many of them at the same time > will > have each interfere with the other. BTW, I've got doubts that even > pure > elaboration tests can interfere, as they work with large (about > 100MBytes) rasters in memory, so loading multiple ones could lead to > memory swapping and cache interferences. Furthermore, the fact that > the > host is a Hudson slave makes it possible that other projects gets > scheduled for a build, making things even more complex. > > What to do? At the moment, the only thing I can think of is to use > Hudson locks to properly serialize performance tests - with a > multi-stage approach I can reduce the "critical section" of tests, > still > resorting to the most brutal solution hurts me. I'd like to know > whether > somebody else has done, or is doing, public work in the area. > > PS There is a very recent (JavaZone '09) presentation about "testing > in > the cloud" which could address some problems, but I think that > JavaZone > '09 slides are not available yet: > > http://javazone.no/incogito09/events/JavaZone%202009/sessions/Continuous%20Performance%20Testing%20in%20the%20Cloud > > In any case, it seems to mostly refer to JEE testing, where one would > expect that indeed the most significant tests are those with multiple > clients in parallel, which is not my primary case. > > PS Yes, I know that parallelizing to 8 different computers instead > than > 8 CPUs of a single computer would be a good idea, but I can't afford > it > :-) In any case, this would bring the problem of having 8 perfectly > identical computers. > > -- > Fabrizio Giudici - Java Architect, Project Manager > Tidalwave s.a.s. - "We make Java work. Everywhere." > weblogs.java.net/blog/fabriziogiudici - www.tidalwave.it/blog > fabrizio.giud...@tidalwave.it - mobile: +39 348.150.6941 > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "The Java Posse" group. To post to this group, send email to javaposse@googlegroups.com To unsubscribe from this group, send email to javaposse+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/javaposse?hl=en -~----------~----~----~----~------~----~------~--~---
