top查看java占用的内存比较多
top - 09:51:24 up 233 days, 20:33, 1 user, load average: 0.03, 0.05, 0.05 Tasks: 175 total, 1 running, 174 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.0 us, 1.3 sy, 0.0 ni, 98.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 8166744 total, 297868 free, 5390512 used, 2478364 buff/cache KiB Swap: 4093048 total, 2895932 free, 1197116 used. 2659996 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 5670 root 20 0 6482256 1.598g 49736 S 0.0 20.5 42:01.18 jsvc 44028 root 20 0 5953100 1.323g 35756 S 0.0 17.0 2:32.59 jsvc 33838 root 20 0 4752112 1.136g 21976 S 0.0 14.6 192:06.62 jsvc 33088 root 20 0 4200396 755288 13756 S 0.0 9.2 208:19.24 jsvc
可见每个占用了大概20%，还是比较高的，因为要部署新的服务，腾内存了
使用jstack查看一下进程的状态，其实也没什么用，不过我昨天刚学的java GC，就试用一下
jstack -F 5670 Attaching to process ID 5670, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.111-b14 Deadlock Detection: No deadlocks found. Thread 52641: (state = BLOCKED) Thread 15362: (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$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 14241: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$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=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 14229: (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$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 13962: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$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=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 12739: (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$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 11133: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$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=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 9556: (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$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 7002: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$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=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 6922: (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$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 6665: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$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=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 5776: (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$ConditionObject.await() @bci=42, line=2039 (Interpreted frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=100, line=1088 (Compiled frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 5775: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2039 (Interpreted frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=100, line=1088 (Compiled frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 5771: (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$ConditionObject.await() @bci=42, line=2039 (Interpreted frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=100, line=1088 (Compiled frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame) Thread 5770: (state = BLOCKED) - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise) - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled frame) - java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2039 (Interpreted frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=100, line=1088 (Compiled frame) - java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take() @bci=1, line=809 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=149, line=1067 (Compiled frame) - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1127 (Interpreted frame) - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=617 (Interpreted frame) - java.lang.Thread.run() @bci=11, line=745 (Interpreted frame)
后边不贴了，总之就是有大量的BLOCKED，这个程序说是bug导致的，下一个版本会修正，另外其他的进程实在IN_NATIVE状态，因为JAVA底层其实是C语言实现的，这个就是在执行C语言的调用，native
我竟然还以为是inactive，Naive
使用jstat分析一下gc，命令格式jstat -gc -t <PID>
jstat -gc -t 5670 Timestamp S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT 484036.7 2048.0 2048.0 0.0 1296.0 694784.0 234952.5 1398272.0 259033.6 59136.0 57496.9 6400.0 6017.4 1023 10.073 3 0.254 10.327
这里面S0C和S1C是两个survivor的容量，S0U和S1U是两个survivor已经使用的容量，EC和EU分别是新生代容量和已用容量，OC和OU是老年代的容量和已用，MC和MU是方法区的容量和使用大小，CCSC和CCSU是压缩类空间容量和使用大小，YGC是minor GC的次数，YGCT是minorGC的总计时间，FGC是major GC的次数，FGCT是major GC的时间，GCT是总共GC的占用时间。
其实这里还可以获取一下内存快照的，方法是
jmap -dump:format=b,file=heap.bin <pid>
file：保存路径及文件名
pid：进程编号（windows通过任务管理器查看，linux通过ps aux查看）
分析工具从http://www.eclipse.org/mat/下载，可惜我这里没有，所以说就算了吧
言归正传，用jmap分析下总的heap，heap就是堆，这里说下，堆和栈是有区别的，堆是存储变量，栈存储的是命令。堆是可以由应用程序来修改和申请空间，栈是由系统来管理的
root@localhost:~# jmap -heap 5670 Attaching to process ID 5670, please wait... Debugger attached successfully. Server compiler detected. JVM version is 25.111-b14 using thread-local object allocation. Parallel GC with 4 thread(s) Heap Configuration: MinHeapFreeRatio = 0 MaxHeapFreeRatio = 100 MaxHeapSize = 2147483648 (2048.0MB) NewSize = 715653120 (682.5MB) MaxNewSize = 715653120 (682.5MB) OldSize = 1431830528 (1365.5MB) NewRatio = 2 SurvivorRatio = 8 MetaspaceSize = 21807104 (20.796875MB) CompressedClassSpaceSize = 1073741824 (1024.0MB) MaxMetaspaceSize = 17592186044415 MB G1HeapRegionSize = 0 (0.0MB) Heap Usage: PS Young Generation Eden Space: capacity = 711458816 (678.5MB) used = 685395312 (653.6439056396484MB) free = 26063504 (24.856094360351562MB) 96.33661100068511% used From Space: capacity = 2097152 (2.0MB) used = 1049696 (1.001068115234375MB) free = 1047456 (0.998931884765625MB) 50.05340576171875% used To Space: capacity = 2097152 (2.0MB) used = 0 (0.0MB) free = 2097152 (2.0MB) 0.0% used PS Old Generation capacity = 1431830528 (1365.5MB) used = 264801120 (252.53402709960938MB) free = 1167029408 (1112.9659729003906MB) 18.493887008393216% used
震惊！运维工程师用jmap分析jvm，竟然……
Eden看起来有点高了，但是其实这么说也是不公平的，Eden（伊甸园）区满了就会触发minorGC，把不活跃的对象清理掉，几次GC后还没有被清理掉的进入survivor，还能幸存的进入老年代，所以如果一个进程说Linux的哪一块内存没有去过，其实潜台词就是他老了(逃
不过Eden还是不能太小了，否则如果被活跃的对象占满了，GC不会处理这些对象，新的对象一直等着进不来，就会造成进程假死了，参考文献
http://www.cnblogs.com/jackchen001/p/6902909.html
或者温和一点，大量的对象放进老生代，导致频繁的full GC，full GC是要暂停程序的，并且会占用大量的CPU，导致性能下降
http://blog.csdn.net/hengyunabc/article/details/24924843
现在就比较简单了，使用java -XX就可以调整了
这里可以看到NewRatio是2，那么就是NewGeneration:OldGeneration = 1:2，new占了1/3的空间，old占了2/3,这里调整一下，把总体从原来的2G调整到1G就可以了，这样老年代空间和新生代空间都缩小了一半，YGC会频繁一点，但是YGC很快，不太会影响，只要老年区不被沾满就行，如果还不放心可以把新生代调大一点，SUN官方推荐新生代为整体的3/8。SurvivoRatio是连个Survivor区与Eden区的大小比值，8就是Eden:Survivor=8:2
java -Xmx1024m -Xmn374m
这样调整后感觉好多了
参考文献
http://www.cnblogs.com/redcreen/archive/2011/05/04/2037057.html