1866 By default, this option is enabled. |
1866 By default, this option is enabled. |
1867 .RE |
1867 .RE |
1868 .TP |
1868 .TP |
1869 .B \f[CB]\-XX:\-UseCompressedOops\f[R] |
1869 .B \f[CB]\-XX:\-UseCompressedOops\f[R] |
1870 Disables the use of compressed pointers. |
1870 Disables the use of compressed pointers. |
1871 By default, this option is enabled, and compressed pointers are used |
1871 By default, this option is enabled, and compressed pointers are used. |
1872 when Java heap sizes are less than 32 GB. |
1872 This will automatically limit the maximum ergonomically determined Java |
1873 When this option is enabled, object references are represented as |
1873 heap size to the maximum amount of memory that can be covered by |
|
1874 compressed pointers. |
|
1875 By default this range is 32 GB. |
|
1876 .RS |
|
1877 .PP |
|
1878 With compressed oops enabled, object references are represented as |
1874 32\-bit offsets instead of 64\-bit pointers, which typically increases |
1879 32\-bit offsets instead of 64\-bit pointers, which typically increases |
1875 performance when running the application with Java heap sizes of less |
1880 performance when running the application with Java heap sizes smaller |
1876 than 32 GB. |
1881 than the compressed oops pointer range. |
1877 This option works only for 64\-bit JVMs. |
1882 This option works only for 64\-bit JVMs. |
1878 .RS |
1883 .PP |
1879 .PP |
1884 It\[aq]s possible to use compressed pointers with Java heap sizes |
1880 It\[aq]s also possible to use compressed pointers when Java heap sizes |
1885 greater than 32 GB. |
1881 are greater than 32 GB. |
|
1882 See the \f[CB]\-XX:ObjectAlignmentInBytes\f[R] option. |
1886 See the \f[CB]\-XX:ObjectAlignmentInBytes\f[R] option. |
1883 .RE |
1887 .RE |
1884 .TP |
1888 .TP |
1885 .B \f[CB]\-XX:\-UseContainerSupport\f[R] |
1889 .B \f[CB]\-XX:\-UseContainerSupport\f[R] |
1886 The VM now provides automatic container detection support, which allows |
1890 The VM now provides automatic container detection support, which allows |
3211 the sizes allocated for the old generation and the young generation. |
3215 the sizes allocated for the old generation and the young generation. |
3212 The size of the heap for the young generation can be set using the |
3216 The size of the heap for the young generation can be set using the |
3213 \f[CB]\-XX:NewSize\f[R] option. |
3217 \f[CB]\-XX:NewSize\f[R] option. |
3214 .RE |
3218 .RE |
3215 .TP |
3219 .TP |
|
3220 .B \f[CB]\-XX:InitialRAMPercentage=\f[R]\f[I]percent\f[R] |
|
3221 Sets the initial amount of memory that the JVM will use for the Java |
|
3222 heap before applying ergonomics heuristics as a percentage of the |
|
3223 maximum amount determined as described in the \f[CB]\-XX:MaxRAM\f[R] |
|
3224 option. |
|
3225 The default value is 1.5625 percent. |
|
3226 .RS |
|
3227 .PP |
|
3228 The following example shows how to set the percentage of the initial |
|
3229 amount of memory used for the Java heap: |
|
3230 .RS |
|
3231 .PP |
|
3232 \f[CB]\-XX:InitialRAMPercentage=5\f[R] |
|
3233 .RE |
|
3234 .RE |
|
3235 .TP |
3216 .B \f[CB]\-XX:InitialSurvivorRatio=\f[R]\f[I]ratio\f[R] |
3236 .B \f[CB]\-XX:InitialSurvivorRatio=\f[R]\f[I]ratio\f[R] |
3217 Sets the initial survivor space ratio used by the throughput garbage |
3237 Sets the initial survivor space ratio used by the throughput garbage |
3218 collector (which is enabled by the \f[CB]\-XX:+UseParallelGC\f[R] and/or |
3238 collector (which is enabled by the \f[CB]\-XX:+UseParallelGC\f[R] and/or |
3219 \f[CB]\-XX:+UseParallelOldGC\f[R] options). |
3239 \f[CB]\-XX:+UseParallelOldGC\f[R] options). |
3220 Adaptive sizing is enabled by default with the throughput garbage |
3240 Adaptive sizing is enabled by default with the throughput garbage |
3367 .B \f[CB]\-XX:MaxNewSize=\f[R]\f[I]size\f[R] |
3387 .B \f[CB]\-XX:MaxNewSize=\f[R]\f[I]size\f[R] |
3368 Sets the maximum size (in bytes) of the heap for the young generation |
3388 Sets the maximum size (in bytes) of the heap for the young generation |
3369 (nursery). |
3389 (nursery). |
3370 The default value is set ergonomically. |
3390 The default value is set ergonomically. |
3371 .RS |
3391 .RS |
|
3392 .RE |
|
3393 .TP |
|
3394 .B \f[CB]\-XX:MaxRAM=\f[R]\f[I]size\f[R] |
|
3395 Sets the maximum amount of memory that the JVM may use for the Java heap |
|
3396 before applying ergonomics heuristics. |
|
3397 The default value is the maximum amount of available memory to the JVM |
|
3398 process or 128 GB, whichever is lower. |
|
3399 .RS |
|
3400 .PP |
|
3401 The maximum amount of available memory to the JVM process is the minimum |
|
3402 of the machine\[aq]s physical memory and any constraints set by the |
|
3403 environment (e.g. |
|
3404 container). |
|
3405 .PP |
|
3406 Specifying this option disables automatic use of compressed oops if the |
|
3407 combined result of this and other options influencing the maximum amount |
|
3408 of memory is larger than the range of memory addressable by compressed |
|
3409 oops. |
|
3410 See \f[CB]\-XX:UseCompressedOops\f[R] for further information about |
|
3411 compressed oops. |
|
3412 .PP |
|
3413 The following example shows how to set the maximum amount of available |
|
3414 memory for sizing the Java heap to 2 GB: |
|
3415 .RS |
|
3416 .PP |
|
3417 \f[CB]\-XX:MaxRAM=2G\f[R] |
|
3418 .RE |
|
3419 .RE |
|
3420 .TP |
|
3421 .B \f[CB]\-XX:MaxRAMPercentage=\f[R]\f[I]percent\f[R] |
|
3422 Sets the maximum amount of memory that the JVM may use for the Java heap |
|
3423 before applying ergonomics heuristics as a percentage of the maximum |
|
3424 amount determined as described in the \f[CB]\-XX:MaxRAM\f[R] option. |
|
3425 The default value is 25 percent. |
|
3426 .RS |
|
3427 .PP |
|
3428 Specifying this option disables automatic use of compressed oops if the |
|
3429 combined result of this and other options influencing the maximum amount |
|
3430 of memory is larger than the range of memory addressable by compressed |
|
3431 oops. |
|
3432 See \f[CB]\-XX:UseCompressedOops\f[R] for further information about |
|
3433 compressed oops. |
|
3434 .PP |
|
3435 The following example shows how to set the percentage of the maximum |
|
3436 amount of memory used for the Java heap: |
|
3437 .RS |
|
3438 .PP |
|
3439 \f[CB]\-XX:MaxRAMPercentage=75\f[R] |
|
3440 .RE |
|
3441 .RE |
|
3442 .TP |
|
3443 .B \f[CB]\-XX:MinRAMPercentage=\f[R]\f[I]percent\f[R] |
|
3444 Sets the maximum amount of memory that the JVM may use for the Java heap |
|
3445 before applying ergonomics heuristics as a percentage of the maximum |
|
3446 amount determined as described in the \f[CB]\-XX:MaxRAM\f[R] option for |
|
3447 small heaps. |
|
3448 A small heap is a heap of approximately 125 MB. |
|
3449 The default value is 50 percent. |
|
3450 .RS |
|
3451 .PP |
|
3452 The following example shows how to set the percentage of the maximum |
|
3453 amount of memory used for the Java heap for small heaps: |
|
3454 .RS |
|
3455 .PP |
|
3456 \f[CB]\-XX:MinRAMPercentage=75\f[R] |
|
3457 .RE |
3372 .RE |
3458 .RE |
3373 .TP |
3459 .TP |
3374 .B \f[CB]\-XX:MaxTenuringThreshold=\f[R]\f[I]threshold\f[R] |
3460 .B \f[CB]\-XX:MaxTenuringThreshold=\f[R]\f[I]threshold\f[R] |
3375 Sets the maximum tenuring threshold for use in adaptive GC sizing. |
3461 Sets the maximum tenuring threshold for use in adaptive GC sizing. |
3376 The largest value is 15. |
3462 The largest value is 15. |
3798 .B \f[CB]\-XX:+FlightRecorder\f[R] |
3884 .B \f[CB]\-XX:+FlightRecorder\f[R] |
3799 Enables the use of Java Flight Recorder (JFR) during the runtime of the |
3885 Enables the use of Java Flight Recorder (JFR) during the runtime of the |
3800 application. |
3886 application. |
3801 Since JDK 8u40 this option has not been required to use JFR. |
3887 Since JDK 8u40 this option has not been required to use JFR. |
3802 .RS |
3888 .RS |
|
3889 .RE |
|
3890 .TP |
|
3891 .B \f[CB]\-XX:InitialRAMFraction=\f[R]\f[I]ratio\f[R] |
|
3892 Sets the initial amount of memory that the JVM may use for the Java heap |
|
3893 before applying ergonomics heuristics as a ratio of the maximum amount |
|
3894 determined as described in the \f[CB]\-XX:MaxRAM\f[R] option. |
|
3895 The default value is 64. |
|
3896 .RS |
|
3897 .PP |
|
3898 Use the option \f[CB]\-XX:InitialRAMPercentage\f[R] instead. |
|
3899 .RE |
|
3900 .TP |
|
3901 .B \f[CB]\-XX:MaxRAMFraction=\f[R]\f[I]ratio\f[R] |
|
3902 Sets the maximum amount of memory that the JVM may use for the Java heap |
|
3903 before applying ergonomics heuristics as a fraction of the maximum |
|
3904 amount determined as described in the \f[CB]\-XX:MaxRAM\f[R] option. |
|
3905 The default value is 4. |
|
3906 .RS |
|
3907 .PP |
|
3908 Specifying this option disables automatic use of compressed oops if the |
|
3909 combined result of this and other options influencing the maximum amount |
|
3910 of memory is larger than the range of memory addressable by compressed |
|
3911 oops. |
|
3912 See \f[CB]\-XX:UseCompressedOops\f[R] for further information about |
|
3913 compressed oops. |
|
3914 .PP |
|
3915 Use the option \f[CB]\-XX:MaxRAMPercentage\f[R] instead. |
|
3916 .RE |
|
3917 .TP |
|
3918 .B \f[CB]\-XX:MinRAMFraction=\f[R]\f[I]ratio\f[R] |
|
3919 Sets the maximum amount of memory that the JVM may use for the Java heap |
|
3920 before applying ergonomics heuristics as a fraction of the maximum |
|
3921 amount determined as described in the \f[CB]\-XX:MaxRAM\f[R] option for |
|
3922 small heaps. |
|
3923 A small heap is a heap of approximately 125 MB. |
|
3924 The default value is 2. |
|
3925 .RS |
|
3926 .PP |
|
3927 Use the option \f[CB]\-XX:MinRAMPercentage\f[R] instead. |
3803 .RE |
3928 .RE |
3804 .TP |
3929 .TP |
3805 .B \f[CB]\-XX:+TraceClassLoading\f[R] |
3930 .B \f[CB]\-XX:+TraceClassLoading\f[R] |
3806 Enables tracing of classes as they are loaded. |
3931 Enables tracing of classes as they are loaded. |
3807 By default, this option is disabled and classes aren\[aq]t traced. |
3932 By default, this option is disabled and classes aren\[aq]t traced. |