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vmtool ​

vmtool利用JVMTI接口，实现查询内存对象，强制GC等功能。

命令选项 ​

命令选项描述
-a, --action <action>指定执行动作，可选值为forceGc, getInstances
-c, --classloader <hash>指定ClassLoader的哈希值
--classLoaderClass <name>指定ClassLoader的类名
--className <name>指定类的名称
-x, --expand <level>指定扩展对象层级，默认1
--express <expression>ognl表达式，默认为instances
--libPath <path>额外库路径
-l, --limit <number>限制返回实例个数，默认10，-1表示无限制
-h, --help帮助

示例 ​

bash
# 强制执行gc
[arthas@17028]$ vmtool -a forceGc 

# 查看java.util.List在内存中的实例 
[arthas@17028]$ vmtool -a getInstances --className java.util.List
@List[][
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
]

# 查看SpringBoot服务实例 
[arthas@17028]$ vmtool -a getInstances --className io.github.passerr.system.application.service.UserService
@UserService[][
    @UserService$$EnhancerBySpringCGLIB$$7fb5d73c[io.github.passerr.system.application.service.UserService@2fe33319],
    @UserService[io.github.passerr.system.application.service.UserService@2fe33319],
]

# 指定ClassLoader查看实例 通过sc -d查询类加载器的哈希值
[arthas@17028]$ vmtool -a getInstances -c 9c7af21 --className io.github.passerr.system.application.service.UserService
@UserService[][
    @UserService$$EnhancerBySpringCGLIB$$7fb5d73c[io.github.passerr.system.application.service.UserService@2fe33319],
    @UserService[io.github.passerr.system.application.service.UserService@2fe33319],
]

# 查询实例并执行ognl表达式
vmtool -a getInstances --className java.util.Random --express "instances[0].seed.value"
@Long[0]
# 强制执行gc
[arthas@17028]$ vmtool -a forceGc 

# 查看java.util.List在内存中的实例 
[arthas@17028]$ vmtool -a getInstances --className java.util.List
@List[][
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
    @ArrayList[isEmpty=false;size=2],
]

# 查看SpringBoot服务实例 
[arthas@17028]$ vmtool -a getInstances --className io.github.passerr.system.application.service.UserService
@UserService[][
    @UserService$$EnhancerBySpringCGLIB$$7fb5d73c[io.github.passerr.system.application.service.UserService@2fe33319],
    @UserService[io.github.passerr.system.application.service.UserService@2fe33319],
]

# 指定ClassLoader查看实例 通过sc -d查询类加载器的哈希值
[arthas@17028]$ vmtool -a getInstances -c 9c7af21 --className io.github.passerr.system.application.service.UserService
@UserService[][
    @UserService$$EnhancerBySpringCGLIB$$7fb5d73c[io.github.passerr.system.application.service.UserService@2fe33319],
    @UserService[io.github.passerr.system.application.service.UserService@2fe33319],
]

# 查询实例并执行ognl表达式
vmtool -a getInstances --className java.util.Random --express "instances[0].seed.value"
@Long[0]