title: What is a good ratio of Java threads to CPUs on Solaris?
body: <p>I have a Java application that has a fixed thread pool of fifteen, the machine, Solaris 10 SPARC, has sixteen CPUs. Adding the pool has greatly increased performance, but I'm wondering if I have too many threads in the pool. Would performance be better with less threads or does Solaris do a good job of thread scheduling.</p>
  
  <p>Say the pool is heavily using fifteen CPUs, then other application threads demand CPU for various reason, concurrent garbage collection is a good example. Now, five CPUs are shared between the pool and other application threads. Then CPUs one through seven become free, will Solaris move the threads sharing time on the busy CPUs to the free CPUs?</p>
  
  <p>If not, would it be better to keep the pool size smaller, so that there are always free CPUs for other application threads? Compounding the issue, CPU usage is very sporadic in the application.</p>