This section describes the settings for OldGen.
Given that the OldGen is composed primarily of cache data of up to about 520 MB, at least 1 GB should be reserved for OldGen. Once -Xmx increases, the OldGen can be increased to 2 GB. 512 MB should be left as a buffer to account for miscellaneous (PermGen, and so on). So the following variations might be applied:
-Xmx2G -Xms1G -XX:NewSIze=512M (OldGen at least 1 GB) -Xmx3G -Xms1G -XX:NewSize=512M (OldGen at least 2 GB) -Xmx4G -Xms2G -XX:NewSize=1G (OldGen at least 2.5 GB) -Xmx6G -Xms3G -XX:NewSize=2G (OldGen at least 3.5 GB) -Xmx8G -Xms4G -XX:NewSize=3G (OldGen at least 4.5 GB)
If you need these levels, you will need to run JConsole (and Java 6) to observe the rate of spillover from Eden space to Survivor to OldGen. If, after the system has been running for a while, the OldGen size stabilizes, then the NewSize can be increased appropriately. The following diagram (using VisualGC) shows how varying the NewSize value affects overall garbage collection activity:
