调试工具
jdk自带的工具
- jmap
- jconsole
- VisualVM
jmap
jmap -histo:live pid列出该进程的所有活动实例统计信息jmap -dump:live,file=test.map pid转储到文件jmap -J-Xms256m -dump:live,file=test.map pid指定内存,防止内存不足jmap -dump:format=b,file=test.map pid转储堆快照
C:>jmap
Usage:
jmap [option] <pid>
(to connect to running process)
jmap [option] <executable <core>
(to connect to a core file)
jmap [option] [server_id@]<remote server IP or hostname>
(to connect to remote debug server)
where <option> is one of:
<none> to print same info as Solaris pmap
-heap to print java heap summary
-histo[:live] to print histogram of java object heap; if the "live"
suboption is specified, only count live objects
-clstats to print class loader statistics
-finalizerinfo to print information on objects awaiting finalization
-dump:<dump-options> to dump java heap in hprof binary format
dump-options:
live dump only live objects; if not specified,
all objects in the heap are dumped.
format=b binary format
file=<file> dump heap to <file>
Example: jmap -dump:live,format=b,file=heap.bin <pid>
-F force. Use with -dump:<dump-options> <pid> or -histo
to force a heap dump or histogram when <pid> does not
respond. The "live" suboption is not supported
in this mode.
-h | -help to print this help message
-J<flag> to pass <flag> directly to the runtime system
mat (Memory Analysis Tool)
- 内存分析工具
jhat (Java Heap Analysis Tool)
- 堆内存分析工具
jhat test.map分析堆快照，并生成html文件jhat -J-Xmx512m test.map指定内存,防止内存不足
C:>jhat
ERROR: No arguments supplied
Usage: jhat [-stack <bool>] [-refs <bool>] [-port <port>] [-baseline <file>] [-debug <int>] [-version] [-h|-help] <file>
-J<flag> Pass <flag> directly to the runtime system. For
example, -J-mx512m to use a maximum heap size of 512MB
-stack false: Turn off tracking object allocation call stack.
-refs false: Turn off tracking of references to objects
-port <port>: Set the port for the HTTP server. Defaults to 7000
-exclude <file>: Specify a file that lists data members that should
be excluded from the reachableFrom query.
-baseline <file>: Specify a baseline object dump. Objects in
both heap dumps with the same ID and same class will
be marked as not being "new".
-debug <int>: Set debug level.
0: No debug output
1: Debug hprof file parsing
2: Debug hprof file parsing, no server
-version Report version number
-h|-help Print this help and exit
<file> The file to read
For a dump file that contains multiple heap dumps,
you may specify which dump in the file
by appending "#<number>" to the file name, i.e. "foo.hprof#3".
All boolean options default to "true"
tips
jps(Java Virtual Machine Process Status Tool )jps命令可以查看当前使用java虚拟机的进程
jstack
jstack可以用来查看Java进程里的线程都在干什么，这通常对于应用没反应，非常慢等等场景都有不小的帮助，jstack默认只能看到Java栈，而jstack -m则可以看到线程的Java栈和native栈，但如果Java方法被编译过，则看不到（然而大部分经常访问的Java方法其实都被编译过）。
C:>jstack
Usage:
jstack [-l] <pid>
(to connect to running process)
jstack -F [-m] [-l] <pid>
(to connect to a hung process)
jstack [-m] [-l] <executable> <core>
(to connect to a core file)
jstack [-m] [-l] [server_id@]<remote server IP or hostname>
(to connect to a remote debug server)
Options:
-F to force a thread dump. Use when jstack <pid> does not respond (process is hung)
-m to print both java and native frames (mixed mode)
-l long listing. Prints additional information about locks
-h or -help to print this help message
jinfo
可以输出并修改运行时的java进程的opts。用处比较简单，用于输出JAVA系统参数及命令行参数。用法是jinfo -opt pid 如：查看2788的MaxPerm大小可以用 jinfo -flag MaxPermSize 2788
where <option> is one of:
-flag <name> to print the value of the named VM flag
-flag [+|-]<name> to enable or disable the named VM flag
-flag <name>=<value> to set the named VM flag to the given value
-flags to print VM flags
-sysprops to print Java system properties
<no option> to print both of the above
-h | -help to print this help message
javah
生成本地方法的头文件