parameter |
illustrate |
1. Heap memory parameter settings |
|
| -Xms or -XX:InitialHeapSize=n |
Set the initial value of the heap Command 1:-Xms2g |
|
-XX:MaxHeapSize=n |
Set the maximum size of the heap area Command 1: -Xmx2gCommand 2: -XX:MaxHeapSize=2048m |
| -XX:NewSize=n | Set young generation size |
| -Xss or -XX:ThreadStackSize=n |
Maximum stack size per thread Command 1: -Xss256k The default stack size is 1M. 128K should be enough. For large stacks, 256K is recommended. If the stack setting is too large, it will lead to thread creation reduce. A small stack setting will result in insufficient depth, and deep recursion will causestack overflow. |
| -Xmn or -XX:MaxNewSize=n |
New generation memory configuration Command 1: -Xmn512m Command 2: -XX:MaxNewSize=512m |
| -XX:SurvivorRatio=n | The size ratio of the two survivor areas and the Eden area The ratio of the Eden area to the two Survivor areas in the young generation. Note that there are two Survivor areas. The ratio of S area and Eden area in the new generation is 1:8, and the two S areas are 2:8. |
| -XX:NewRatio=n | The proportion of the new generation and the old generation Indicates the new generation: old generation = 1:2, that is, the old generation occupies 2/3 of the entire heap; default value = 2 If -Xms==-Xmx and -Xmn is set, there is no need to set this parameter. |
| -Duser.timezone=GMT+08 | Specify time zone |
| ‐Dfile.encoding=UTF‐8 | Specify default file encoding |
2. Garbage collector settings |
|
| -XX:+PrintGC |
Simple printing of GC logs |
| -XX:+PrintGCDetails | Print GC logs in detail |
| -XX:+PrintHeapAtGC | Print detailed stack information before and after GC |
| -XX:+PrintGCTimeStamps | When GC occurs, the time when GC occurs is additionally output. This output time is the time offset after the virtual machine is started. |
| -XX:+PrintGCDateStamps | When GC occurs, date printing with time zone |
| -XX:+PrintGCApplicationConcurrentTime | Print the uninterrupted execution time of the application before each garbage collection |
| -XX:+PrintGCApplicationStoppedTime | Print application pause times due to GC |
| -XX:+PrintReferenceGC | Track soft references, weak references, virtual references and Finalize queues within the system |
2.1 GC recycling log printing |
|
| -Xloggc:log/gc.log | Specify the file path for gc log output. JDK8 begins to support the use of placeholders such as %p and %t to specify GC output files. Represent the process pid and startup timestamp respectively. For example: -Xloggc:/data/gclog/gc.log fixed path name generation -Xloggc:/data/gclog/gc-%t.log generated based on time -Xloggc:/data/gclog/gc-%p.log generated based on process pid |
| -XX:+UseGCLogFileRotation | Rolling log generation After the log file reaches a certain size, another file will be generated, and -Xloggc must be configured |
| -XX:NumberOfGCLogFiles=n | -XX:NumberOfGCLogFiles=4 Number of rolling GC log files, default 0, no rolling, need to configure UseGCLogFileRotation, set to 0 to indicate triggering only through jcmd command |
| -XX:GCLogFileSize=n | -XX:GCLogFileSize=100k GC file rolling size, UseGCLogFileRotation needs to be configured. Setting it to 0 means it is only triggered by the jcmd command. |
2.2 Heap memory overflow configuration |
|
| -XX:+HeapDumpOnOutOfMemoryError | Export the entire heap information when memory overflows, allowing the JVM to output heap information when it encounters an OOM exception, and set the file address of the heap memory overflow snapshot output through the (-XX:+HeapDumpPath) parameter -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=./log/dump/ |
| -XX:HeapDumpPath | Specify the storage path of the export heap |
| -XX:OnOutOfMemoryError=“” | Using this parameter, we can customize a script after the system OOM, which can be used to send email alarm information, restart the system, etc. -XX:OnOutOfMemoryError="/opt/local/bin/alert.sh" |
| -XX:+HeapDumpBeforeFullGC | Implement dump before Full GC -XX:HeapDumpPath=/logs/Set the path where Dump is saved |
| -XX:+HeapDumpAfterFullGC | Implement dump after Full GC -XX:HeapDumpPath=/logs/Set the path where Dump is saved |
2.3 Garbage collector configuration |
|
| -XX:+UseSerialGC | Enables the use of a serial garbage collector. This is usually the best choice for small and simple applications that don't require any special functionality for garbage collection. By default, this option is disabled and the collector is automatically selected based on the machine's configuration and the type of JVM. |
| -XX:+UseParallelGC | Allows the use of a parallel cleaning garbage collector (also known as a throughput collector) to improve application performance by utilizing multiple processors. By default, this option is disabled and the collector is automatically selected based on the computer's configuration and the type of JVM. If enabled, this option is |
| -XX:+UseParalledlOldGC | allows the parallel garbage collector to be used for a full GC. By default, this option is disabled. Enabling this will automatically enable this-XX:+UseParallelGCoption. |
| -XX:+UseConcMarkSweepGC | allows the use of the CMS garbage collector for the old generation. Oracle recommends that you use the CMS garbage collector when the spam ( By default, this option is disabled and the collector is automatically selected based on the computer's configuration and the type of JVM. When this option is enabled, this option will |
| -XX:+UseParNewGC | allows the use of parallel threads for collection in the young generation. By default, this option is disabled. It is automatically enabled when setting the-XX:+UseConcMarkSweepGC option. Use-XX:+UseParNewGCwithout option-XX:+UseConcMarkSweepGC option is deprecated in JDK 8 |
| -XX:+UseG1GC | Allows the use of a garbage-first (G1) garbage collector. It is a server-style garbage collector targeted at multi-processor machines with large amounts of RAM. It meets GC pause time targets with high probability while maintaining good throughput. The G1 collector is recommended for applications requiring large heaps (approximately 6 GB in size or larger) and limited GC latency requirements (stable and predictable pause times below 0.5 seconds) |
| -XX:ParallelGCThreads=n | Number of GC parallel execution threads -XX:ParallelGCThreads=16 |
3. Auxiliary instructions (view or modify a certain configuration of the running JVM) |
|
| jinfo -flag parameter pid | Check whether the HeapDumpOnOutOfMemoryError configuration is enabled jinfo -flag HeapDumpOnOutOfMemoryError 10001 Modify HeapDumpOnOutOfMemoryError configuration (-off + on) jinfo -flag +HeapDumpOnOutOfMemoryError 10001 |
| -XX:+PrintFlagsFinal | View jvm parameter configuration -XX:+PrintFlagsFinal |grep GC View GC related parameter configurations |
| -XX:+PrintCommandLineFlags | Print parameters that have been set by the user or the current virtual machine -XX:+PrintCommandLineFlags -version View the initial size of the GC heap and the GC collector type |
4.Default configuration of JVM startup parameters for JDK8 |
|
|
|
4. Disable and discard parameter options |
|
| -Xincgc Enable incremental garbage collection. This option is deprecated in JDK 8 and does not need to be replaced. -Xrun libname Loads the specified debugging/analysis library. This option has been superseded by this option -XX: CMSIncrementalDutyCycle = Percentage Sets the percentage of time (0 to 100) between secondary collections that the concurrent collector is allowed to run. This option has been deprecated in JDK 8 without replacement after the option was deprecated. -XX: CMSIncrementalDutyCycleMin = Percentage Sets the percentage of time between secondary collections (0 to 100), which -XX：+ CMSIncrementalMode Enables the incremental mode of the CMS collector. This option is deprecated in JDK 8 and has no replacement, along with other options -XX: CMSIncrementalOffset = Percentage Sets the percentage of time (0 to 100) that the incremental mode duty cycle shifts to the right during the period between minor sets. This option has been deprecated in JDK 8 without replacement after the option was deprecated. -XX：+ CMSIncrementalPacing Enables automatic adjustment of the incremental mode duty cycle based on statistics collected while the JVM is running. This option has been deprecated in JDK 8 without replacement after the option was deprecated. -XX: CMSIncrementalSafetyFactor = Percentage Sets the percentage of time (0 to 100) used to add conservatism when calculating duty cycle. This option has been deprecated in JDK 8 without replacement after the option was deprecated. -XX：CMSInitiatingPermOccupancyFraction = Percentage Set the percentage of permanent generation occupancy (0 to 100) that starts GC. This option is deprecated in JDK 8 and does not need to be replaced. -XX：MaxPermSize = size Sets the maximum permanent generation space size in bytes. This option is deprecated in JDK 8 and replaced by the -XX：PermSize = size Sets the space (in bytes) allocated for permanent generation, which will trigger garbage collection if exceeded. This option is deprecated in JDK 8 and replaced by this option. -XX：+ UseSplitVerifier Allows splitting the verification process. By default, this option was enabled in previous versions, and verification is divided into two phases: type reference (performed by the compiler) and type checking (performed by the JVM runtime). This option was deprecated in JDK 8 and validation is now split by default and cannot be disabled. -XX：+ UseStringCache Enable caching of commonly allocated strings. This option has been removed from JDK 8 and does not need to be replaced. |
|
[Java] JDK8 jvm parameter configuration and description
Guess you like
Origin blog.csdn.net/smallbirdnq/article/details/132967867
Recommended
Ranking