Java分析工具
jstack
jstack [option] pid
jstack命令行工具，可以连接到特定进程或核心文件，并打印连接到JVM的所有线程的栈信息，包括Java线程和JVM内部线程，以及可选的本地栈进程（本地方法）。该工具还可以用于检测死锁。
调用jsadebugd可以获得远程主机上的某个进程的堆栈信息。
-l选项，命令jstack工具查找堆内被持有的同步对象，并打印java.util.concurrent.locks的信息。如果不指定这个选项，则只对象监视器。
线程的dump信息也可以通过编程的方式获得（Thread.getAllStackTraces）。
如果进程被挂起，对该进程调用jstack命令，将无法获得响应。你可以使用-F选项强制进行栈信息dump。
jstack工具也可以打印混合栈信息，即，它除了可以打印java栈外还会打印本地栈帧。所谓的本地栈帧是指与VM代码或JNI/native代码相关的C/C++帧。要打印混合栈，你需要使用-m选项。
jinfo
jinfo [option] pid
jinfo工具用于打印某个jvm进程的java配置信息。配置信息是由Java系统变量、Java虚拟机命令行参数组成的。如果给定的进程是64字节的虚拟机，那么也许你会需要指定-J-d64选项，比如：
jinfo -J-d64 pid
如果你想查看一个运行中的JVM的classpath、系统变量、命令行参数等信息，你可以使用jinfo得到。
jstat
jstat [generalOption | outputOption vmid [interval[s|ms] [count]]]
jstat工具可以展现一个被增强的JVM的性能相关数据。目标JVM利用它的虚拟机的标识符或者vmid指定。
generalOption
一个通用的命令行选项：
- -help: 展现帮助信息
- -options: 展现统计选项列表。
outputOptions
一个或多个输出选项，包含一个单独的statOption，加上-t,-h,-J选项中的任意选项。
如果你没有指定通用选项，那么你可以指定输出选项，输出选项决定了jstat的输出的格式和内容。
输出被格式化为表格，每列用空格隔开，首行包含了描述列的标题信息。
命令行选项：
- -h n:每n个样本打印一次列首（标题），n必须为正数，默认为0，表示仅打印一次。
- -t:将时间戳作为第一列进行展示，时间戳为当前时间减去JVM启动时间。
- -J javaOption:向java应用启动程序传递javaOption。
不建议写脚本来解析jstat的输出内容，因为它的格式很有可能会在未来的发行版中被改动。
statOption
-
class:类加载器的性能表现数据
- compiler:HotSpot的JIT编译器的性能表现数据
- gc:被垃圾回收的堆的性能表现数据
- gccapacity:内存分代的容量以及已用空间。
- gccause:GC的数据摘要，以及上一次垃圾回收事件的触发原因
- gcnew:新代的性能表现数据
- gcnewcapacity:新代的容量和已用空间
- gcold:永久代和年老代的性能表现数据
- gcoldcapacity:年老代的大小数据
- gcpermcapacity:永久代的大小数据
- gcutil: gc数据摘要
- printcompilation:HotSpot方法编译数据。
class
| Column | Description |
|---|---|
| Loaded | Number of classes loaded. |
| Bytes | Number of Kbytes loaded. |
| Unloaded | Number of classes unloaded. |
| Bytes | Number of Kbytes unloaded. |
| Time | Time spent performing class load and unload operations. |
compiler
| Column | Description |
|---|---|
| Compiled | Number of compilation tasks performed. |
| Failed | Number of compilation tasks that failed. |
| Invalid | Number of compilation tasks that were invalidated. |
| Time | Time spent performing compilation tasks. |
| FailedType | Compile type of the last failed compilation. |
| FailedMethod | Class name and method for the last failed compilation. |
gc
| Column | Description |
|---|---|
| S0C | Current survivor space 0 capacity (KB). |
| S1C | Current survivor space 1 capacity (KB). |
| S0U | Survivor space 0 utilization (KB). |
| S1U | Survivor space 1 utilization (KB). |
| EC | Current eden space capacity (KB). |
| EU | Eden space utilization (KB). |
| OC | Current old space capacity (KB). |
| OU | Old space utilization (KB). |
| PC | Current permanent space capacity (KB). |
| PU | Permanent space utilization (KB). |
| YGC | Number of young generation GC Events. |
| YGCT | Young generation garbage collection time. |
| FGC | Number of full GC events. |
| FGCT | Full garbage collection time. |
| GCT | Total garbage collection time. |
gccapacity
| Column | Description |
|---|---|
| NGCMN | Minimum new generation capacity (KB). |
| NGCMX | Maximum new generation capacity (KB). |
| NGC | Current new generation capacity (KB). |
| S0C | Current survivor space 0 capacity (KB). |
| S1C | Current survivor space 1 capacity (KB). |
| EC | Current eden space capacity (KB). |
| OGCMN | Minimum old generation capacity (KB). |
| OGCMX | Maximum old generation capacity (KB). |
| OGC | Current old generation capacity (KB). |
| OC | Current old space capacity (KB). |
| PGCMN | Minimum permanent generation capacity (KB). |
| PGCMX | Maximum Permanent generation capacity (KB). |
| PGC | Current Permanent generation capacity (KB). |
| PC | Current Permanent space capacity (KB). |
| YGC | Number of Young generation GC Events. |
| FGC | Number of Full GC Events. |
gccause
| Column | Description |
|---|---|
| LGCC | Cause of last Garbage Collection. |
| GCC | Cause of current Garbage Collection. |
gcnew
| Column | Description |
|---|---|
| S0C | Current survivor space 0 capacity (KB). |
| S1C | Current survivor space 1 capacity (KB). |
| S0U | Survivor space 0 utilization (KB). |
| S1U | Survivor space 1 utilization (KB). |
| TT | Tenuring threshold. |
| MTT | Maximum tenuring threshold. |
| DSS | Desired survivor size (KB). |
| EC | Current eden space capacity (KB). |
| EU | Eden space utilization (KB). |
| YGC | Number of young generation GC events. |
| YGCT | Young generation garbage collection time. |
gcnewcapacity
| Column | Description |
|---|---|
| NGCMN | Minimum new generation capacity (KB). |
| NGCMX | Maximum new generation capacity (KB). |
| NGC | Current new generation capacity (KB). |
| S0CMX | Maximum survivor space 0 capacity (KB). |
| S0C | Current survivor space 0 capacity (KB). |
| S1CMX | Maximum survivor space 1 capacity (KB). |
| S1C | Current survivor space 1 capacity (KB). |
| ECMX | Maximum eden space capacity (KB). |
| EC | Current eden space capacity (KB). |
| YGC | Number of young generation GC events. |
| FGC | Number of Full GC Events. |
gcold
| Column | Description |
|---|---|
| PC | Current permanent space capacity (KB). |
| PU | Permanent space utilization (KB). |
| OC | Current old space capacity (KB). |
| OU | old space utilization (KB). |
| YGC | Number of young generation GC events. |
| FGC | Number of full GC events. |
| FGCT | Full garbage collection time. |
| GCT | Total garbage collection time. |
gcoldcapacity
| Column | Description |
|---|---|
| OGCMN | Minimum old generation capacity (KB). |
| OGCMX | Maximum old generation capacity (KB). |
| OGC | Current old generation capacity (KB). |
| OC | Current old space capacity (KB). |
| YGC | Number of young generation GC events. |
| FGC | Number of full GC events. |
| FGCT | Full garbage collection time. |
| GCT | Total garbage collection time. |
gcpermcapacity
| Column | Description |
|---|---|
| PGCMN | Minimum permanent generation capacity (KB). |
| PGCMX | Maximum permanent generation capacity (KB). |
| PGC | Current permanent generation capacity (KB). |
| PC | Current permanent space capacity (KB). |
| YGC | Number of young generation GC events. |
| FGC | Number of full GC events. |
| FGCT | Full garbage collection time. |
| GCT | Total garbage collection time. |
gcutil
| Column | Description |
|---|---|
| S0 | Survivor space 0 utilization as a percentage of the space's current capacity. |
| S1 | Survivor space 1 utilization as a percentage of the space's current capacity. |
| E | Eden space utilization as a percentage of the space's current capacity. |
| O | Old space utilization as a percentage of the space's current capacity. |
| P | Permanent space utilization as a percentage of the space's current capacity. |
| YGC | Number of young generation GC events. |
| YGCT | Young generation garbage collection time. |
| FGC | Number of full GC events. |
| FGCT | Full garbage collection time. |
| GCT | Total garbage collection time. |
printcompilation
| Column | Description |
|---|---|
| Compiled | Number of compilation tasks performed by the most recently compiled method. |
| Size | Number of bytes of bytecode of the most recently compiled method. |
| Type | Compilation type of the most recently compiled method. |
| Method | Class name and method name identifying the most recently compiled method. Class name uses "/" instead of "." as namespace separator. Method name is the method within the given class. The format for these two fields is consistent with the HotSpot - XX:+PrintComplation option. |
jmap
jmap [option] pid
jmap工具用于显示一个给定进程的共享对象内存映射后堆内存细节。如果给定进程为64字节虚拟机，你可能需要指定-J-d64选项。
选项：
- <无选项>:jmap仅显示共享对象映射。对于虚拟机加载的所有共享对象，开始地址、映射大小、共享对象的全文件路径都会被显示。
- -dump:[live,]format=b,file=<filename>: 按照hprof的二进制格式将java堆dump到指定文件中。如果指定了live，将仅dump存活对象。之后你可以通过jhat（Java Heap Analysis Tool）来阅读生成文件。
- -finalizerinfo: 显示等待析构的对象的信息。
- -heap: 显示堆摘要，使用的GC算法，堆配置以及分代信息。
- -histo[:live]: 显示描述堆的直方图。对于每个类，实例的数目，占用的内存的字节数，以及全限定类名都会被显示。虚拟机内部类名带有'*'前缀。如果指定了live，那么仅存活对象被计数。
- -permstat:显示永久代中类加载器的数据。对于每个类加载器，它的名字，存活状态，地址，父加载器，以及它所加载过的类的数目和大小都会被显示。此外，常量池中的字符串的数目和大小也会被显示。
- -F: 强制，如果pid进程没有响应，需要带上这个参数（使用这个参数就不能带上live参数）。
- -h: 显示帮助信息。
- -help: 显示帮助信息
- -J<flag>: 传递<flag>到JVM。