JVM自带监控工具

Posted 2021-01-01 yifansj

1. jstat

jstat -gcutil 67008 5s 3

查看pid为67008的进程的堆内存各个区域占用总容量百分比，

5秒刷新一次，共查询3次

运行结果如下:

说明:

• S0: Survivor0(新生代Survivor)是空的
• S1: Survivor1(新生代Survivor)是空的
• E: Eden(新生代Eden)占用0.38%
• O: Old(老年代)占用48.24%
• M:
• CCS:
• YGC: Young GC==> Minor GC ==> 新生代GC的次数
• YGCT: YGC 耗时0.578秒
• FGC: Full GC==>老年代GC的次数
• FGCT: FGC总耗时1.067秒
• GCT: 所有GC总耗时1.645秒

2. jinfo

jinfo -flags process_id

查看jvm的参数

3. jmap

jmap -heap 1234  (1234为进程号)

打印堆信息

-heap：打印heap空间的概要，这里可以粗略的检验heap空间的使用情况。

例：
jmap -heap 12345
输出：
Attaching to process ID 2657, please wait...
Debugger attached successfully.
Client compiler detected.
JVM version is 1.5.0_16-b02
 
using thread-local object allocation.
Mark Sweep Compact GC
 
Heap Configuration:
   MinHeapFreeRatio = 40
   MaxHeapFreeRatio = 70
   MaxHeapSize      = 67108864 (64.0MB)
   NewSize          = 655360 (0.625MB)
   MaxNewSize       = 4294901760 (4095.9375MB)
   OldSize          = 1441792 (1.375MB)
   NewRatio         = 12
   SurvivorRatio    = 8
   PermSize         = 8388608 (8.0MB)
   MaxPermSize      = 67108864 (64.0MB)
 
Heap Usage:
New Generation (Eden + 1 Survivor Space):----------------------------------------新生代区
   capacity = 4521984 (4.3125MB)
   used     = 1510200 (1.4402389526367188MB)
   free     = 3011784 (2.8722610473632812MB)
   33.39684527853261% used
Eden Space:--------------------------------------------------------------------伊甸园区

   capacity = 4063232 (3.875MB)
   used     = 1495992 (1.4266891479492188MB)
   free     = 2567240 (2.4483108520507812MB)
   36.81778446320565% used
From Space:-------------------------------------------------------------------年轻代（幸存者乐园1）

   capacity = 458752 (0.4375MB)
   used     = 14208 (0.0135498046875MB)
   free     = 444544 (0.4239501953125MB)
   3.0970982142857144% used
To Space:-----------------------------------------------------------------------------年轻代（幸存者乐园2）
   capacity = 458752 (0.4375MB)
   used     = 0 (0.0MB)
   free     = 458752 (0.4375MB)
   0.0% used

concurrent mark-sweep generation:-------------------------------------------------老年代
capacity = 8589934592 (8192.0MB)
used = 0 (0.0MB)
free = 8589934592 (8192.0MB)
0.0% used

Perm Generation:----------------------------------------------------------------------永久代
   capacity = 11796480 (11.25MB)
   used     = 11712040 (11.169471740722656MB)
   free     = 84440 (0.08052825927734375MB)
   99.28419325086806% used

-histo：这里会生成一个类的统计报表，此表简单无比，如显示什么类有多少个实例，共占了多少字节等，如下：

Size    Count   Class description
-------------------------------------------------------
8394352 105     long[]
8293192 57202   char[]
7834776 14157   byte[]
6713592 53743   * ConstMethodKlass
4194320 1       com.xjawa.cms5server.Kontent[]
4055072 12319   int[]
3291104 85082   * SymbolKlass
3016040 53743   * MethodKlass
2774936 4253    * ConstantPoolKlass
1871480 4253    * InstanceKlassKlass
1811808 3990    * ConstantPoolCacheKlass
1488672 62028   java.lang.String
1203280 13258   java.lang.Object[]