JVM调优工具

当没有VisualVM等可视化工具进行JVM内存分析，可以使用以下JDK自带的工具进行分析。

jps

查看java进程内部id
第一列：java进程内部id（1、238），第二列：主类的全类名

bash-4.2# jps -l
1 org.apache.catalina.startup.Bootstrap
238 sun.tools.jps.Jps

jstat

查看JVM各内存区域使用状况及GC信息

bash-4.2# jstat -gccause 1
  S0     S1     E      O      M     CCS    YGC     YGCT    FGC    FGCT     GCT    LGCC                 GCC                 
 53.09   0.00  96.00  60.70  94.23  91.42    444    1.794     8    0.723    2.517 Allocation Failure   No GC 

jmap

可以查看堆内存的使用情况以及可以转储堆文件

bash-4.2# jmap -heap 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.382-b05

using thread-local object allocation.
Mark Sweep Compact GC

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 394264576 (376.0MB)
   NewSize                  = 8388608 (8.0MB)
   MaxNewSize               = 131399680 (125.3125MB)
   OldSize                  = 16777216 (16.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
New Generation (Eden + 1 Survivor Space):
   capacity = 85590016 (81.625MB)
   used     = 80954640 (77.20436096191406MB)
   free     = 4635376 (4.4206390380859375MB)
   94.58420944798047% used
Eden Space:
   capacity = 76087296 (72.5625MB)
   used     = 75909264 (72.39271545410156MB)
   free     = 178032 (0.1697845458984375MB)
   99.76601612968346% used
From Space:
   capacity = 9502720 (9.0625MB)
   used     = 5045376 (4.8116455078125MB)
   free     = 4457344 (4.2508544921875MB)
   53.09401939655172% used
To Space:
   capacity = 9502720 (9.0625MB)
   used     = 0 (0.0MB)
   free     = 9502720 (9.0625MB)
   0.0% used
tenured generation:
   capacity = 189595648 (180.8125MB)
   used     = 115075904 (109.74493408203125MB)
   free     = 74519744 (71.06756591796875MB)
   60.695435372018665% used

54241 interned Strings occupying 5439040 bytes.

jstack

查看线程状态及线程调用栈轨迹

bash-4.2# jstack -F 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.382-b05
Deadlock Detection:

No deadlocks found.

Thread 373: (state = BLOCKED)
 - java.lang.Thread.sleep(long) @bci=0 (Compiled frame; information may be imprecise)
 - sun.net.www.http.KeepAliveCache.run() @bci=3, line=172 (Interpreted frame)
 - java.lang.Thread.run() @bci=11, line=750 (Interpreted frame)


Thread 348: (state = BLOCKED)


Thread 150: (state = BLOCKED)
 - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise)
 - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame)
 - java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2039 (Compiled frame)
 - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=24, line=1081 (Compiled frame)
 - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame)
 - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1074 (Compiled frame)
 - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1134 (Interpreted frame)
 - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=624 (Interpreted frame)
 - java.lang.Thread.run() @bci=11, line=750 (Interpreted frame)

jcmd

bash-4.2# jcmd 1 GC.heap_info
1:
 def new generation   total 83584K, used 39663K [0x00000000e8800000, 0x00000000ee2b0000, 0x00000000f0550000)
  eden space 74304K,  44% used [0x00000000e8800000, 0x00000000ea817400, 0x00000000ed090000)
  from space 9280K,  73% used [0x00000000ed090000, 0x00000000ed7348c0, 0x00000000ed9a0000)
  to   space 9280K,   0% used [0x00000000ed9a0000, 0x00000000ed9a0000, 0x00000000ee2b0000)
 tenured generation   total 185152K, used 115966K [0x00000000f0550000, 0x00000000fba20000, 0x0000000100000000)
   the space 185152K,  62% used [0x00000000f0550000, 0x00000000f768fad0, 0x00000000f768fc00, 0x00000000fba20000)
 Metaspace       used 123452K, capacity 130620K, committed 130816K, reserved 1163264K
  class space    used 14981K, capacity 16350K, committed 16384K, reserved 1048576K