jmap命令样例 ：
[root@localhost ~]# jmap -histo 6913|head -20 num #instances #bytes class name ---------------------------------------------- 1: 1864966 113459432 [C 2: 201846 49201192 [B 3: 1597065 38329560 java.lang.String 4: 117477 15037056 org.zhangyoubao.thriftdef.UserUsefulInfo 5: 47104 11072048 [I 6: 268631 8596192 java.util.HashMap$Entry 7: 48812 7451760 <constMethodKlass> 8: 100683 6443712 com.mysql.jdbc.ConnectionPropertiesImpl$BooleanConnectionProperty 9: 48812 6257856 <methodKlass> 10: 4230 5271640 <constantPoolKlass> 11: 159491 5103712 java.util.Hashtable$Entry 12: 120226 4809040 org.zhangyoubao.common.cache.adv.Node 13: 127027 4064864 java.util.concurrent.ConcurrentHashMap$HashEntry 14: 230433 3686928 java.lang.Integer 15: 3765 3049824 <constantPoolCacheKlass> 16: 20917 3012048 com.mysql.jdbc.Field 17: 4230 2943840 <instanceKlassKlass> 其中 [C = char[] , [B = byte[] , [S = short[] , [I = int[] , [[I = int[][] 。 |
jhat: 虚拟机堆转存快照分析工具
jhat 命令用于与jmap搭配使用，用来分析jmap生成的dump文件。jhat内置了一个微型的HTTP/HTML服务器，生成的dump文件的分析结果后，可以在浏览器查看。
jhat命令格式 ：
jmap filename
jhat命令样例 ：
[root@localhost ~]# jhat html_intercept_server.dump
Reading from html_intercept_server.dump...
Dump file created Wed Nov 23 13:05:33 CST 2016
Snapshot read, resolving...
Resolving 203681 objects...
Chasing references, expect 40 dots........................................
Eliminating duplicate references........................................
Snapshot resolved.
Started HTTP server on port 7000
Server is ready.
jstack:java线程堆栈跟踪工具
jstack用于生成虚拟机当前时刻的线程快照。线程快照就是当前虚拟机每一条线程正在执行的方法堆栈计划，生成线程快照的主要目的是定位线程长时间停顿的原因。在线程停顿的时候，通过jstack来查看没有响应的线程在后台做些什么事情，或者等待着什么资源。
jstack命令格式 ：
jstack [option] vmid
jstack其他选项 ：
-F 当正常输出的请求不被响应的时候，强制输出线程堆栈；
-l 除了显示堆栈外，显示关于锁的附加信息；
-m 如果调用本地方法，可以显示C/C++的堆栈。
jstack命令样例 ：
[root@localhost ~]# jstack 29577|head -20 2016-11-23 12:58:23 Full thread dump OpenJDK Server VM (24.91-b01 mixed mode): "pool-1-thread-7261" prio=10 tid=0x0893a400 nid=0x6b0d waiting on condition [0x652ad000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x75b5b400> (a java.util.concurrent.SynchronousQueue$TransferStack) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226) at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(SynchronousQueue.java:460) at java.util.concurrent.SynchronousQueue$TransferStack.transfer(SynchronousQueue.java:359) at java.util.concurrent.SynchronousQueue.poll(SynchronousQueue.java:942) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) "service_hot_lscs-0" daemon prio=10 tid=0x6982dc00 nid=0x6aeb waiting on condition [0x64ce1000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at org.zhangyoubao.video.client.runner.SimpleVideoRunner.doWork(SimpleVideoRunner.java:150) |
