JVM监控工具介绍
28 October 2013
jps
列出所有的jvm实例
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$ jps
13877 Jps
10019 Bootstrap
4364 activemq.jar
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$ jps host
列出远程服务器上的JVM实例,采用RMI协议，默认连接端口为1099
jmap
用来显示Java进程的内存映射(也能分析Java core文件)
默认视图
jmap最简单的用法是查看连接到进程里的本地类库。除非你的应用程序里有很多JNI代码, 否则这种用法通常没什么用。
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$ jmap 10019
Attaching to process ID 10019, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 23.25-b01
0x0000000000400000 7K /home/microloan/software/jdk1.7.0_25/bin/java
0x00000034c3e00000 153K /lib64/ld-2.12.so
0x00000034c4200000 1877K /lib64/libc-2.12.so
0x00000034c4600000 584K /lib64/libm-2.12.so
0x00000034c4a00000 22K /lib64/libdl-2.12.so
0x00000034c4e00000 142K /lib64/libpthread-2.12.so
0x00000034c5600000 45K /lib64/librt-2.12.so
0x00000034c6200000 111K /lib64/libresolv-2.12.so
0x00000034ce600000 91K /lib64/libgcc_s-4.4.6-20110824.so.1
0x00007f7880f42000 474K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libt2k.so
0x00007f7881934000 490K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libfontmanager.so
0x00007f78822b1000 26K /lib64/libnss_dns-2.12.so
0x00007f78884c1000 250K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libsunec.so
0x00007f7888708000 36K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/headless/libmawt.so
0x00007f788890f000 759K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libawt.so
0x00007f7888be2000 44K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libmanagement.so
0x00007f7888dea000 107K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libnet.so
0x00007f78901e3000 89K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libnio.so
0x00007f789a4de000 120K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libzip.so
0x00007f789a6f9000 64K /lib64/libnss_files-2.12.so
0x00007f789a91f000 214K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libjava.so
0x00007f789ab4a000 63K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/libverify.so
0x00007f789ae59000 13190K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/server/libjvm.so
0x00007f789bb7c000 103K /home/microloan/software/jdk1.7.0_25/jre/lib/amd64/jli/libjli.so
堆视图
使用-heap选项时,jmap会抓取进程当前的堆快照。在输出结果中能看到构成Java进程堆内存的基本参数。
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$ jmap -heap 10019
Attaching to process ID 10019, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 23.25-b01
using thread-local object allocation.
Parallel GC with 4 thread(s)
Heap Configuration:
MinHeapFreeRatio = 40
MaxHeapFreeRatio = 70
MaxHeapSize = 1073741824 (1024.0MB)
NewSize = 1310720 (1.25MB)
MaxNewSize = 17592186044415 MB
OldSize = 5439488 (5.1875MB)
NewRatio = 2
SurvivorRatio = 8
PermSize = 536870912 (512.0MB)
MaxPermSize = 536870912 (512.0MB)
G1HeapRegionSize = 0 (0.0MB)
Heap Usage:
PS Young Generation
Eden Space:
capacity = 350093312 (333.875MB)
used = 274149616 (261.44944763183594MB)
free = 75943696 (72.42555236816406MB)
78.30758446479548% used
From Space:
capacity = 3801088 (3.625MB)
used = 98304 (0.09375MB)
free = 3702784 (3.53125MB)
2.586206896551724% used
To Space:
capacity = 3604480 (3.4375MB)
used = 0 (0.0MB)
free = 3604480 (3.4375MB)
0.0% used
PS Old Generation
capacity = 715849728 (682.6875MB)
used = 209051048 (199.36661529541016MB)
free = 506798680 (483.32088470458984MB)
29.20320282638984% used
PS Perm Generation
capacity = 536870912 (512.0MB)
used = 141163656 (134.62415313720703MB)
free = 395707256 (377.37584686279297MB)
26.29377990961075% used
36088 interned Strings occupying 3954552 bytes.
柱状视图
柱状视图显示了系统中每个类型的实例(还有一些内部实体)占用的内存量。各个类型按使 用内存多少排列,这样就比较容易看到最大的内存。
当然,如果所有内存都交给了框架和平台类,这里可能就没你什么事了。但如果真有一个你 的类,有了这些信息便能更好地干预它的内存占用。
| $ jmap -histo 10019 | head -30 |
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num #instances #bytes class name
----------------------------------------------
1: 228765 175874592 [I
2: 508052 129038624 [B
3: 707707 71626144 [C
4: 245171 37640784 <constMethodKlass>
5: 245171 33355304 <methodKlass>
6: 22498 25107264 <constantPoolKlass>
7: 22498 17390320 <instanceKlassKlass>
8: 651709 15641016 java.lang.String
9: 18016 13946432 <constantPoolCacheKlass>
10: 88801 7104080 java.lang.reflect.Method
11: 74206 6517832 [Ljava.util.HashMap$Entry;
12: 197260 6312320 java.util.HashMap$Entry
13: 121133 4845320 java.util.LinkedHashMap$Entry
14: 109182 4367280 java.util.HashMap$ValueIterator
15: 159152 4024816 [Ljava.lang.String;
16: 69208 3680112 [Ljava.lang.Object;
17: 44330 3191760 java.util.regex.Pattern
18: 5365 3107120 <methodDataKlass>
19: 46070 2948480 java.util.regex.Matcher
20: 24025 2875640 java.lang.Class
21: 49420 2767520 java.util.HashMap
22: 112061 2689464 java.io.File
23: 109185 2620440 org.apache.catalina.LifecycleEvent
24: 44025 2465400 [Ljava.util.regex.Pattern$GroupHead;
25: 109184 2211856 [Lorg.apache.catalina.Container;
26: 64608 2067456 java.util.concurrent.ConcurrentHashMap$HashEntry
27: 39373 1961768 [[I
柱状图模式下还能看到其他有意思的事情,这次指定-histo:live选项。这是告诉jmap只 处理存活对象,而不是整个堆(jmap默认会处理所有对象,也包括还没被收集的垃圾)。让我们 看看这次输出什么:
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$ jmap -histo:live 10019|head -30
num #instances #bytes class name
----------------------------------------------
1: 74512 47870936 [B
2: 244687 37588560 <constMethodKlass>
3: 244687 33289480 <methodKlass>
4: 241228 31651544 [C
5: 22264 24880992 <constantPoolKlass>
6: 22264 17239360 <instanceKlassKlass>
7: 17782 13773984 <constantPoolCacheKlass>
8: 237034 5688816 java.lang.String
9: 171257 5480224 java.util.HashMap$Entry
10: 64024 5121920 java.lang.reflect.Method
11: 51623 4688640 [Ljava.util.HashMap$Entry;
12: 5364 3106664 <methodDataKlass>
13: 23791 2849368 java.lang.Class
14: 52890 2774632 [Ljava.lang.Object;
15: 66549 2661960 java.util.LinkedHashMap$Entry
16: 60908 1949056 java.util.concurrent.ConcurrentHashMap$HashEntry
17: 37817 1892168 [[I
18: 30760 1882104 [S
19: 28266 1710304 [I
20: 28325 1586200 java.util.HashMap
21: 56713 1550616 [Ljava.lang.String;
22: 19744 1263616 java.util.LinkedHashMap
23: 24731 1187088 org.apache.catalina.loader.ResourceEntry
24: 16361 1047104 java.net.URL
25: 37258 894192 java.util.ArrayList
26: 22105 884200 java.lang.ref.SoftReference
27: 1510 869760 <objArrayKlassKlass>
注意输出的变化查看那些类是消耗内存的主要力量。
使用jmap时应该稍微谨慎点。进行该操作时JVM还在运行(如果你不走运,还有可能在读 取快照期间做了垃圾回收),所以你应该多运行几次,特别是在你看到任何奇怪或太好的结果时。
产生离线导出文件
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$ jmap -dump:live,format=b,file=heap.hprof 10019
导出结果可以用来做离线分析,可以留给jmap以后自己用,也可以留给Oracle的jhat等工具做高级分析.
VisualVM
VisualVM是Oracle JVM自带的可视化工具。它是插件架构,采用标准配置,比JConsole用起来更方便。
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$jvisualvm
如图所示:
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