找出给定 java 进程的 -Xms 和 -Xmx 变量值的命令？

Question

我有一个 java 程序，我运行并用 jps 计算出它的进程 ID。

如何查看此 java 进程的 -Xms 和 -Xmx 变量的值？

Answer 1

您可以使用 jps 并从命令行执行此操作：

jps # shows pids
jps -v <pid> # shows params
jps -v <localhost:pid> # the host must be indicated

如果这还不够，您可以在程序内部以编程方式执行此操作以检查 maximum amount of memory that the Java virtual machine will attempt to use:

Runtime.getRuntime().maxMemory()

你也可以使用 class MemoryUsage 来获取可用于内存管理的初始、已用和最大数量。

MemoryMXBean memoryBean = ManagementFactory.getMemoryMXBean();
    memoryBean.getHeapMemoryUsage().getMax()
    memoryBean.getHeapMemoryUsage().getUsed()
    memoryBean.getHeapMemoryUsage().getInit()

Answer 2

尝试

jcmd <PID> VM.command_line
jcmd <PID> VM.flags

Answer 3

我认为 jmap 命令会给你想要的一切。
用法：jmap -heap {pid}

root@BobServerStation:/usr/local $ jmap -heap 3280
Attaching to process ID 3280, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.65-b04

using thread-local object allocation.
Parallel GC with 8 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 0
   MaxHeapFreeRatio = 100
   MaxHeapSize      = 4116709376 (3926.0MB)
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 85983232 (82.0MB)
   G1HeapRegionSize = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 65011712 (62.0MB)
   used     = 42273152 (40.3148193359375MB)
   free     = 22738560 (21.6851806640625MB)
   65.0239021547379% used
From Space:
   capacity = 10485760 (10.0MB)
   used     = 10479760 (9.994277954101562MB)
   free     = 6000 (0.0057220458984375MB)
   99.94277954101562% used
To Space:
   capacity = 10485760 (10.0MB)
   used     = 0 (0.0MB)
   free     = 10485760 (10.0MB)
   0.0% used
PS Old Generation
   capacity = 171442176 (163.5MB)
   used     = 376368 (0.3589324951171875MB)
   free     = 171065808 (163.1410675048828MB)
   0.21953057805332568% used
PS Perm Generation
   capacity = 22020096 (21.0MB)
   used     = 15401488 (14.688003540039062MB)
   free     = 6618608 (6.3119964599609375MB)
   69.94287400018601% used

8464 interned Strings occupying 699456 bytes.

找出给定 java 进程的 -Xms 和 -Xmx 变量值的命令？

Command to find out -Xms and -Xmx variable values for a given java process?

java

jvm

java-opts