Statement : JVM VM Performance Options
| Option and Default Value | Description |
|---|---|
| -XX:+AggressiveOpts | Turn on point performance compiler optimizations that are expected to be default in upcoming releases. (Introduced in 5.0 update 6.) |
| -XX:CompileThreshold=10000 | Number of method invocations/branches before compiling [-client: 1,500] |
| -XX:LargePageSizeInBytes=4m | Sets the large page size used for the Java heap. (Introduced in 1.4.0 update 1.) [amd64: 2m.] |
| -XX:MaxHeapFreeRatio=70 | Maximum percentage of heap free after GC to avoid shrinking. |
| -XX:MaxNewSize=size | Maximum size of new generation (in bytes). Since 1.4, MaxNewSize is computed as a function of NewRatio. [1.3.1 Sparc: 32m; 1.3.1 x86: 2.5m.] |
| -XX:MaxPermSize=64m | Size of the Permanent Generation. [5.0 and newer: 64 bit VMs are scaled 30% larger; 1.4 amd64: 96m; 1.3.1 -client: 32m.] |
| -XX:MinHeapFreeRatio=40 | Minimum percentage of heap free after GC to avoid expansion. |
| -XX:NewRatio=2 | Ratio of old/new generation sizes. [Sparc -client: 8; x86 -server: 8; x86 -client: 12.]-client: 4 (1.3) 8 (1.3.1+), x86: 12] |
| -XX:NewSize=2m | Default size of new generation (in bytes) [5.0 and newer: 64 bit VMs are scaled 30% larger; x86: 1m; x86, 5.0 and older: 640k] |
| -XX:ReservedCodeCacheSize=32m | Reserved code cache size (in bytes) - maximum code cache size. [Solaris 64-bit, amd64, and -server x86: 2048m; in 1.5.0_06 and earlier, Solaris 64-bit and amd64: 1024m.] |
| -XX:SurvivorRatio=8 | Ratio of eden/survivor space size [Solaris amd64: 6; Sparc in 1.3.1: 25; other Solaris platforms in 5.0 and earlier: 32] |
| -XX:TargetSurvivorRatio=50 | Desired percentage of survivor space used after scavenge. |
| -XX:ThreadStackSize=512 | Thread Stack Size (in Kbytes). (0 means use default stack size) [Sparc: 512; Solaris x86: 320 (was 256 prior in 5.0 and earlier); Sparc 64 bit: 1024; Linux amd64: 1024 (was 0 in 5.0 and earlier); all others 0.] |
| -XX:+UseBiasedLocking | Enable biased locking. For more details, see this tuning example. (Introduced in 5.0 update 6.) [5.0: false] |
| -XX:+UseFastAccessorMethods | Use optimized versions of Get |
| -XX:-UseISM | Use Intimate Shared Memory. [Not accepted for non-Solaris platforms.] For details, see Intimate Shared Memory. |
| -XX:+UseLargePages | Use large page memory. (Introduced in 5.0 update 5.) For details, see Java Support for Large Memory Pages. |
| -XX:+UseMPSS | Use Multiple Page Size Support w/4mb pages for the heap. Do not use with ISM as this replaces the need for ISM. (Introduced in 1.4.0 update 1, Relevant to Solaris 9 and newer.) [1.4.1 and earlier: false] |
| -XX:+UseStringCache | Enables caching of commonly allocated strings. |
| -XX:AllocatePrefetchLines=1 | Number of cache lines to load after the last object allocation using prefetch instructions generated in JIT compiled code. Default values are 1 if the last allocated object was an instance and 3 if it was an array. |
| -XX:AllocatePrefetchStyle=1 | Generated code style for prefetch instructions. 0 - no prefetch instructions are generate*d*, 1 - execute prefetch instructions after each allocation, 2 - use TLAB allocation watermark pointer to gate when prefetch instructions are executed. |
| -XX:+UseCompressedStrings | Use a byte[] for Strings which can be represented as pure ASCII. (Introduced in Java 6 Update 21 Performance Release) |
| -XX:+OptimizeStringConcat | Optimize String concatenation operations where possible. (Introduced in Java 6 Update 20) |
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