Java GC tuning for strings

问题:

Profiling the application I figured out that there are a lot of strings on heap.

In my situation, strings are created on heap and not interned and they are not literals.

Are there are specific GC tuning techniques to follow when the number of strings in the application are very high.

I stumbled across the GC settings -XX:+UseCompressedStrings or -XX+UseStringCache but not sure this will help. Did any body try these settings?

java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)

回答1:

Related to -XX:+UseCompressedStrings, you should have a look at this question: Support for Compressed Strings being Dropped in HotSpot JVM?

And, related to -XX+UseStringCache, have a look at : JVM -XX:+StringCache argument?

Btw. Java 7 comes with nice features that allow tuning of String cache when using the interned Strings. See -XX:+PrintSTringTableStatistics and -XX:StringTableSize=n. This way you can optimize the String cache size.