See also Tuning Garbage Collection with the 5.0 Java Virtual Machine. This may have worked before exact garbage collection became popular, but this is just not a good idea for any modern Java Virtual Machines. Don't use object pools! Using object pools will fool the collector into thinking objects are live when they really aren't. To work around this, some programs keep an 'object pool', saving previously allocated objects in some freelist-like data structure and reusing them instead of allocating new ones. Many systems have less efficient memory management than in HotSpot. If you are worried about the number of garbage collections, but less worried about pause times, then increasing the heap should cause the number of full garbage collections to decrease, this is especially true if you increase the size of the eden space as well. Using the above as an example, you can do the following in 1.4 and later: In 1.4 and later, MaxNewSize has been effectively set to infinity, and NewRatio can be used instead to set the value of the new generation.

NewRatio (the ratio between the young/old generations) has values of 2 on Sparc Server, 12 on client Intel, and 8 everywhere else, as you can quickly determine, this is superseded by MaxNewSize's defaults (rendering NewRatio ineffective for even moderately sized heaps). For 1.3, MaxNewSize is set to 32mb on Sparc, 2.5mb on Intel based machines. Which will dedicate 1/3rd of the memory to eden. If you currently invoke with something like: For most programs, collecting eden is much faster than other generations because most objects die young. For some applications a very large eden helps, for others it will increase the times of minor collections. If your application requires more memory than you can adjust the size of the eden (young generation space) with -XX:NewSize=. A larger heap will cause garbage collection pauses to increase because there is more heap to scan.

Next, you might try decreasing the amount of heap used. For most programs this results in shorter pauses, although throughput is usually worse. This uses the incremental garbage collection algorithm, which attempts to collect a fraction of the heap instead of the entire thing at once. There are several things to try in this arena.

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