查找給定java進程的-Xms和-Xmx變量值的命令？

Question

我有一個java程序，我跑了，並找出它的進程id與jps。

如何查看此java進程的-Xms和-Xmx變量的值？

Answer 1

嘗試

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

Answer 2

可以使用JPS和命令行做到這一點：

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

如果這還不夠，你可以做到這一點編程裏面的程序檢查maximum amount of memory that the Java virtual machine will attempt to use：

Runtime.getRuntime().maxMemory() 

和你也可以使用類MemoryUsage來獲取可用於內存管理的初始，已用和最大安裝。

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

Answer 3

我認爲jmap命令會給你你想要的一切。
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.