查看,更新VM诊断相关的参数 `vmoption -h`{{execute T2}} ```bash [arthas@48]$ vmoption -h USAGE: vmoption [-h] [name] [value] SUMMARY: Display, and update the vm diagnostic options. Examples: vmoption vmoption PrintGCDetails vmoption PrintGCDetails true WIKI: https://arthas.aliyun.com/doc/vmoption OPTIONS: -h, --help this help VMOption name VMOption value ``` ## 使用参考 ### 查看所有的option: `vmoption`{{execute T2}} ```bash [arthas@56963]$ vmoption KEY VALUE ORIGIN WRITEABLE --------------------------------------------------------------------------------------------- HeapDumpBeforeFullGC false DEFAULT true HeapDumpAfterFullGC false DEFAULT true HeapDumpOnOutOfMemory false DEFAULT true Error HeapDumpPath DEFAULT true CMSAbortablePrecleanW 100 DEFAULT true aitMillis CMSWaitDuration 2000 DEFAULT true CMSTriggerInterval -1 DEFAULT true PrintGC false DEFAULT true PrintGCDetails true MANAGEMENT true PrintGCDateStamps false DEFAULT true PrintGCTimeStamps false DEFAULT true PrintGCID false DEFAULT true PrintClassHistogramBe false DEFAULT true foreFullGC PrintClassHistogramAf false DEFAULT true terFullGC PrintClassHistogram false DEFAULT true MinHeapFreeRatio 0 DEFAULT true MaxHeapFreeRatio 100 DEFAULT true PrintConcurrentLocks false DEFAULT true ``` ### 查看指定的option `vmoption PrintGCDetails`{{execute T2}} ```bash [arthas@56963]$ vmoption PrintGCDetails KEY VALUE ORIGIN WRITEABLE --------------------------------------------------------------------------------------------- PrintGCDetails false MANAGEMENT true ``` ### 更新指定的option `vmoption PrintGCDetails true`{{execute T2}} ```bash [arthas@56963]$ vmoption PrintGCDetails true Successfully updated the vm option. PrintGCDetails=true ``` 此时,切换到arthas demo 运行所在的`Terminal`,使用`Ctrl+c`退出,发现比之前多打印了GC垃圾回收信息: ```bash Heap def new generation total 10432K, used 5682K [0x00000000f4800000, 0x00000000f5350000, 0x00000000f8550000) eden space 9280K, 61% used [0x00000000f4800000, 0x00000000f4d8cad0, 0x00000000f5110000) from space 1152K, 0% used [0x00000000f5110000, 0x00000000f5110000, 0x00000000f5230000) to space 1152K, 0% used [0x00000000f5230000, 0x00000000f5230000, 0x00000000f5350000) tenured generation total 22992K, used 13795K [0x00000000f8550000, 0x00000000f9bc4000, 0x0000000100000000) the space 22992K, 59% used [0x00000000f8550000, 0x00000000f92c8cc8, 0x00000000f92c8e00, 0x00000000f9bc4000) Metaspace used 14926K, capacity 15128K, committed 15360K, reserved 1062912K class space used 1895K, capacity 1954K, committed 2048K, reserved 1048576K ```