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查看，更新VM诊断相关的参数
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`vmoption -h`{{execute T2}}
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```bash
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[arthas@48]$ vmoption -h
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USAGE:
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vmoption [-h] [name] [value]
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SUMMARY:
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Display, and update the vm diagnostic options.
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Examples:
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vmoption
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vmoption PrintGCDetails
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vmoption PrintGCDetails true
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WIKI:
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https://arthas.aliyun.com/doc/vmoption
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OPTIONS:
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-h, --help this help
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<name> VMOption name
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<value> VMOption value
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```
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## 使用参考
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### 查看所有的option：
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`vmoption`{{execute T2}}
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```bash
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[arthas@56963]$ vmoption
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|
|
KEY VALUE ORIGIN WRITEABLE
|
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|
---------------------------------------------------------------------------------------------
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|
HeapDumpBeforeFullGC false DEFAULT true
|
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|
HeapDumpAfterFullGC false DEFAULT true
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|
HeapDumpOnOutOfMemory false DEFAULT true
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|
Error
|
|
|
HeapDumpPath DEFAULT true
|
|
|
CMSAbortablePrecleanW 100 DEFAULT true
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|
|
aitMillis
|
|
|
CMSWaitDuration 2000 DEFAULT true
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|
CMSTriggerInterval -1 DEFAULT true
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PrintGC false DEFAULT true
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PrintGCDetails true MANAGEMENT true
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PrintGCDateStamps false DEFAULT true
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|
PrintGCTimeStamps false DEFAULT true
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|
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
|
|
|
```
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|
|
### 查看指定的option
|
|
|
|
|
|
`vmoption PrintGCDetails`{{execute T2}}
|
|
|
|
|
|
```bash
|
|
|
[arthas@56963]$ vmoption PrintGCDetails
|
|
|
KEY VALUE ORIGIN WRITEABLE
|
|
|
---------------------------------------------------------------------------------------------
|
|
|
PrintGCDetails false MANAGEMENT true
|
|
|
```
|
|
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|
|
|
### 更新指定的option
|
|
|
|
|
|
`vmoption PrintGCDetails true`{{execute T2}}
|
|
|
|
|
|
```bash
|
|
|
[arthas@56963]$ vmoption PrintGCDetails true
|
|
|
Successfully updated the vm option.
|
|
|
PrintGCDetails=true
|
|
|
```
|
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|
|
|
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
|
|
|
```
|