JVM Heap size - How

[Ramu Nur]

Hi
Is there a standard technique to set the JVM heap size for an application? Or is it a trail-and-error (after profiling) with some start up values?

Thanks

[Deepak Bala]

Trail and error mostly. Some apps hog memory and others dont. It depends on how state is maintained; what is cached; how large the cache is; what the purge policy for caches are; etc etc.

A load and performance test usually highlights the limits of CPU / memory / Threads. A good rule of thumb is to add some buffer to the max limit (say 20%. But 20% of what number ? That can be a factor too).

[chander shivdasani]

Ya, i agree to Deepak. Its mainly by trial error.
One thing to look is how often does JVM do GC. Make sure its not spending most of its time doing GC.