bilibili-JVM学习笔记21 java 工具
The Java Virtual Machine Specification - Java SE 8 Edition
JVM学习笔记18 字节码知识总结
JVM学习笔记19 JVM内存空间
JVM学习笔记20 jvisualvm
基于 java 1.8.0
jmap与jstat工具实战分析 67
➜ ~ jmap -h
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
jps -l
jmap -clstats [pid]
类加载器关系
jmap -heap [pid]
内存空间与GC
➜ ~ jstat -h
-h requires an integer argument
Usage: jstat -help|-options
jstat -<option> [-t] [-h<lines>] <vmid> [<interval> [<count>]]
Definitions:
<option> An option reported by the -options option
<vmid> Virtual Machine Identifier. A vmid takes the following form:
<lvmid>[@<hostname>[:<port>]]
Where <lvmid> is the local vm identifier for the target
Java virtual machine, typically a process id; <hostname> is
the name of the host running the target Java virtual machine;
and <port> is the port number for the rmiregistry on the
target host. See the jvmstat documentation for a more complete
description of the Virtual Machine Identifier.
<lines> Number of samples between header lines.
<interval> Sampling interval. The following forms are allowed:
<n>["ms"|"s"]
Where <n> is an integer and the suffix specifies the units as
milliseconds("ms") or seconds("s"). The default units are "ms".
<count> Number of samples to take before terminating.
-J<flag> Pass <flag> directly to the runtime system.
jstat -gc [pid]
内存空间分布，包括元空间
jcmd命令实战讲解 68
➜ ~ jcmd -h
Usage: jcmd <pid | main class> <command ...|PerfCounter.print|-f file>
or: jcmd -l
or: jcmd -h
command must be a valid jcmd command for the selected jvm.
Use the command "help" to see which commands are available.
If the pid is 0, commands will be sent to all Java processes.
The main class argument will be used to match (either partially
or fully) the class used to start Java.
If no options are given, lists Java processes (same as -p).
PerfCounter.print display the counters exposed by this process
-f read and execute commands from the file
-l list JVM processes on the local machine
-h this help