【视频笔记】JVM内存越来越高，查了2周，发现是堆外内存泄露！

top查看负载情况

检查堆与非堆

通过jcmd与jstat观察JVM堆使用情况

## jcmd pid GC.heap_info

[service@localhost ~]$ jcmd 11264 GC.heap_info
11264:
def new generation total 4928K, used 795K [0x00000000f0a00000, 0x00000000f0f50000, 0x00000000f5c00000)
eden space 4416K, 18% used [0x00000000f0a00000, 0x00000000f0ac6cb8, 0x00000000f0e50000)
from space 512K, 0% used [0x00000000f0e50000, 0x00000000f0e50000, 0x00000000f0ed0000)
to space 512K, 0% used [0x00000000f0ed0000, 0x00000000f0ed0000, 0x00000000f0f50000)
tenured generation total 10944K, used 0K [0x00000000f5c00000, 0x00000000f66b0000, 0x0000000100000000)
the space 10944K, 0% used [0x00000000f5c00000, 0x00000000f5c00000, 0x00000000f5c00200, 0x00000000f66b0000)
Metaspace used 127K, committed 320K, reserved 1114112K
class space used 3K, committed 128K, reserved 1048576K

## jstat -gcutil pid 时间间隔

[service@localhost ~]$ jstat -gcutil 11264 3000
S0 S1 E O M CCS YGC YGCT FGC FGCT CGC CGCT GCT
0.00 0.00 18.01 0.00 - - 0 0.000 0 0.000 - - 0.000

## jcmd其他参数，可以通过jcmd pid help显示

[service@localhost ~]$ jcmd 11264
11264:
The following commands are available:
Compiler.CodeHeap_Analytics
Compiler.codecache
Compiler.codelist
Compiler.directives_add
Compiler.directives_clear
Compiler.directives_print
Compiler.directives_remove
Compiler.perfmap
Compiler.queue
GC.class_histogram
GC.finalizer_info
GC.heap_dump
GC.heap_info
GC.run
GC.run_finalization
JFR.check
JFR.configure
JFR.dump
JFR.start
JFR.stop
JVMTI.agent_load
JVMTI.data_dump
ManagementAgent.start
ManagementAgent.start_local
ManagementAgent.status
ManagementAgent.stop
System.native_heap_info
System.trim_native_heap
Thread.print
VM.cds
VM.class_hierarchy
VM.classloader_stats
VM.classloaders
VM.command_line
VM.dynlibs
VM.events
VM.flags
VM.info
VM.log
VM.metaspace
VM.native_memory
VM.print_touched_methods
VM.set_flag
VM.stringtable
VM.symboltable
VM.system_properties
VM.systemdictionary
VM.uptime
VM.version
help