> From: Robinson, Eric [eric.robin...@psmnv.com] > Is there a way to tell what the optimal > heap size is for our application, and whether the current small size is > effecting performance (aside from trial-and-error or repeated > benchmarking with tools like jmeter)?
Smaller heap sizes may lead to more frequent garbage collection, which costs CPU cycles* and hence affects performance. If your app is spending much of its time in the garbage collector, increasing heap would help - but it's then a process of trial-and-error to work out what the "optimal" size is, as it's a trade-off between %CPU spent in garbage collection and memory. As a sketch, I'd turn on some of the GC monitoring in the virtual machine and see if you can get a feel for how much time it's spending in the GC. Most of my apps are well below 1%, though I have one (.Net app) that spends c. 98% of its time in the GC as it loads state from disk. You also need to decide what's "good enough". The difference in "real-world" performance between spending 0.1% and 1% in the GC is negligible; the difference between 10% and 90% is rather obvious! - Peter * Some of the cycles would be spent no matter when the garbage happened to be collected; others are overhead each time, though GC algorithms have improved a lot and the overhead's far lower than it used to be. --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
