记录一下查看问题的步骤：
1 jps
找出程序的PID
2 jstack ${PID}
查看线程dump，发现rabbitMQ的consumer worker线程block住了：
"Thread-33" prio=10 tid=0x00002aaac8013000 nid=0x3264 waiting for monitor entry [0x00000000437e4000]
java.lang.Thread.State: BLOCKED (on object monitor)
at org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3525)
- waiting to lock <0x000000072039ce18> (a java.lang.Object)
at org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3505)
at com.xiaomi.miliao.mt.fulltextindex.UserIndexUpdater.updatePlUserIndex(UserIndexUpdater.java:229)
- locked <0x0000000711ab59c8> (a java.lang.Object)
at com.xiaomi.miliao.mt.fulltextindex.SearcherDelegate.updatePlUserIndex(SearcherDelegate.java:522)
at com.xiaomi.miliao.mt.fulltextindex.MessageQueueDelegate$PlUserIndexMessageHandler.handleMessage(MessageQueueDelegate.java:342)
at com.xiaomi.miliao.rabbitmq.ConsumerWorker.run(ConsumerWorker.java:107)
at java.lang.Thread.run(Thread.java:662)
这个线程的状态是wating for monitor entry，但是它在等待这个锁（0x000000072039ce18）已经被下面的这个线程占有了，而且下面的这个线程一直在run，没有返回。根据它的栈信息，查看java.io.FileDescriptor.sync方法，怀疑是系统IO很繁忙，一直没有返回。
"Thread-24" prio=10 tid=0x00002aaac8007000 nid=0x3257 runnable [0x00000000431d8000]
java.lang.Thread.State: RUNNABLE
at java.io.FileDescriptor.sync(Native Method)
at org.apache.lucene.store.FSDirectory.sync(FSDirectory.java:321)
at org.apache.lucene.index.IndexWriter.startCommit(IndexWriter.java:4801)
at org.apache.lucene.index.IndexWriter.prepareCommit(IndexWriter.java:3461)
at org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3534)
- locked <0x000000072039ce18> (a java.lang.Object)
at org.apache.lucene.index.IndexWriter.commit(IndexWriter.java:3505)
at com.xiaomi.miliao.mt.fulltextindex.UserIndexUpdater.updatePlUserIndex(UserIndexUpdater.java:229)
- locked <0x0000000711d6b558> (a java.lang.Object)
at com.xiaomi.miliao.mt.fulltextindex.SearcherDelegate.updatePlUserIndex(SearcherDelegate.java:522)
at com.xiaomi.miliao.mt.fulltextindex.MessageQueueDelegate$PlUserIndexMessageHandler.handleMessage(MessageQueueDelegate.java:342)
at com.xiaomi.miliao.rabbitmq.ConsumerWorker.run(ConsumerWorker.java:107)
at java.lang.Thread.run(Thread.java:662)
3 ssh到指定服务器，查看cpu负载
top -d 5 五秒刷新一次，然后按1，查看所有的cpu的情况，没有发现异常，但是发现我的服务确实很占cpu啊，给力！lucene确实需要优化，赶紧切换到sensei吧
[root@MT1-10 logs]# top -d 5
top - 20:13:51 up 439 days, 16:15, 7 users, load average: 4.56, 4.82, 4.84
Tasks: 244 total, 1 running, 243 sleeping, 0 stopped, 0 zombie
Cpu0 : 17.6%us, 1.6%sy, 0.0%ni, 73.6%id, 7.2%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu1 : 6.6%us, 1.4%sy, 0.0%ni, 6.0%id, 85.8%wa, 0.0%hi, 0.2%si, 0.0%st
Cpu2 : 5.6%us, 0.8%sy, 0.0%ni, 84.1%id, 9.6%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu3 : 4.4%us, 0.4%sy, 0.0%ni, 95.2%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu4 : 3.0%us, 0.6%sy, 0.0%ni, 93.8%id, 2.6%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu5 : 2.2%us, 0.6%sy, 0.0%ni, 94.4%id, 2.8%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu6 : 2.2%us, 0.2%sy, 0.0%ni, 95.6%id, 2.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu7 : 15.0%us, 2.4%sy, 0.0%ni, 70.1%id, 12.2%wa, 0.0%hi, 0.4%si, 0.0%st
Cpu8 : 5.4%us, 0.6%sy, 0.0%ni, 91.6%id, 2.2%wa, 0.0%hi, 0.2%si, 0.0%st
Cpu9 : 5.2%us, 1.2%sy, 0.0%ni, 66.9%id, 26.7%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu10 : 2.6%us, 0.6%sy, 0.0%ni, 92.4%id, 4.4%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu11 : 6.2%us, 0.8%sy, 0.0%ni, 93.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu12 : 2.4%us, 0.4%sy, 0.0%ni, 95.4%id, 1.8%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu13 : 11.8%us, 1.2%sy, 0.0%ni, 84.7%id, 2.4%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu14 : 2.2%us, 0.2%sy, 0.0%ni, 97.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Cpu15 : 35.8%us, 5.2%sy, 0.0%ni, 41.8%id, 12.8%wa, 0.2%hi, 4.2%si, 0.0%st
Mem: 32956180k total, 32849076k used, 107104k free, 547628k buffers
Swap: 6144820k total, 228k used, 6144592k free, 18353516k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12681 root 18 0 5168m 2.4g 13m S 129.3 7.7 1675:27 java
4 使用iostat -d -x 1 100，查看系统io的使用情况(-d 是查看disk, -c是查看cpu), -x是查看更多信息，1是1秒刷新一次，100是查看一百次
[root@MT1-10 logs]# iostat -d -x 1 1
Linux 2.6.18-194.el5 (MT1-10) 10/09/2012
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
cciss/c0d0 0.00 776.00 3.00 259.00 24.00 11360.00 43.45 51.73 352.21 3.82 100.10
cciss/c0d0p1
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
cciss/c0d0p2
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
cciss/c0d0p3
0.00 23.00 0.00 3.00 0.00 208.00 69.33 0.18 61.00 61.00 18.30
cciss/c0d0p4
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
cciss/c0d0p5
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
cciss/c0d0p6
0.00 753.00 3.00 256.00 24.00 11152.00 43.15 51.55 355.59 3.86 100.10
具体名咯解析可查看
http://wenku.baidu.com/view/5991f2781711cc7931b7168c.html
发现cciss/c0d0p6的%util达到了100%，太繁忙了。
平均IO请求的队列长度avgqu-sz是51.55
平均使用的扇区数量是43.15
平均每个IO的等待时间的355.59毫秒
说明这快磁盘已经出现性能瓶颈了！
使用iopp可查看每个进程的IO情况！