Solaris 10 screams running Java. Competitive benchmarks do a good job highlighting this,just take a look at the latest SPECjbb2005 and SPECjappserver2004 results. I have noticed some fundamental differences in "Out of the Box" tuning when comparing Solaris and Linux. When running Java server applications, Solaris 10 default tuning is general purpose and tuned for moderate thread counts similar to a time shared system. This in many ways is an indication of the maturity of the platform. Linux, on the other hand, is specfically tuned for high thread counts and performance suffers when running low thread counts. A good example of this behavior can be seen comparing SPECjbb2005 results. Below are two results run on the exact same hardware, only differing the OS and minor JVM tuning (the heap tuning has minimal performance impact). SPECjbb2005 on Sun Fire X4200 running Solaris 10 Update 1, 49,097 SPECjbb2005 bops, 49,097 SPECjbb2005 bops/JVM SPECjbb2005 on Sun Fire X4200 running Red Hat EL 4, 43,076 SPECjbb2005 bops, 43,076 SPECjbb2005 bops/JVM Running SPECjbb2005 on identical hardware with optimal tuning parameters Solaris 10 is 14% faster than Linux. SPECjbb2005 on small x64 hardware runs only a moderate number of threads, in the above example to peak application thread count is 8. What tuning can be applied when running high thread counts on Solaris 10 x86? Here's two quick tuning steps you can try with your application. 1. If you're running many threads and performing socket I/O, try libumem.so. When launching your application within a shell script, set the following environment variable. LD_PRELOAD=/usr/lib/libumem.so;export LD_PRELOAD 2. Tune the Solaris scheduler. Simple scheduler tuning can yield significant performance gains, especially with highly threaded short lived applications. Try the FX scheduling class: priocntl -c FX -e java class_name Try the IA scheduling class: priocntl -c IA -e java class_name Every application is different and true performance is always defined by each individual running their own application. If you run into problems or have questions about Java on Solaris performance visit the java.net performance forum or feel free to send me a comment. Fine print SPEC disclosure: SPECjbb2005 Sun Fire X4200 on Solaris 10 (2 chips, 4 cores, 4 threads) 49,097 bops, 49,097 bops/JVM, SPECjbb2005 Sun Fire X4200 on Red Hat EL 4 (2 chips, 2 cores, 2 threads) 43,076 bops, 43,076 bops/JVM. SPEC™ and the benchmark name SPECjbb2005™ are trademarks of the Standard Performance Evaluation Corporation. Competitive benchmark results stated above reflect results published on www.spec.org as of February 17, 2006. For the latest SPECjbb2005 benchmark results, visit http://www.spec.org/osg/jbb2005.