> Generate a flame graph using [async-profiler](https://github.com/jvm-profiling-tools/async-profiler)

[profiler command](https://arthas.aliyun.com/en/doc/profiler.html) supports generate flame graph for application hotspots.

The basic usage of the `profiler`{{}} command is `profiler action [actionArg]`{{}}

### View all supported actions

`profiler actions`{{execute T2}}

### View version

`profiler version`{{execute T2}}

### Start profiler

`profiler start --event cpu`{{execute T2}}

> By default, the sample event is `cpu`{{}} . Can be specified with the `--event`{{}} parameter.

### Get the number of samples collected

`profiler getSamples`{{execute T2}}

### View profiler status

`profiler status`{{execute T2}}

### Stop profiler

#### Generating html format results

By default, the result file is `html`{{}} format. You can also specify it with the `--format`{{}} parameter:

`profiler stop --format html`{{execute T2}}

Or use the file name name format in the `--file`{{}} parameter. For example, `--file /tmp/result.html`{{}} .

`profiler stop --file /root/arthas-output/result.html`{{execute T2}}

### View profiler results under arthas-output via browser

By default, arthas uses http port 8563, [click to open]({{TRAFFIC_HOST1_8563}}/arthas-output/) and enter username `arthas` and password `arthas` to view the `arthas-output`{{}} directory below Profiler results:

![](https://arthas.aliyun.com/doc/_images/arthas-output.jpg)

Click to view specific results:

![](https://arthas.aliyun.com/doc/_images/arthas-output-svg.jpg)

### Profiler supported events

`profiler list`{{execute T2}}

Under different platforms and different OSs, the supported events are different. For example, under macos:

```bash
$ profiler list
Basic events:
  cpu
  alloc
  lock
  wall
  itimer
```

Under linux

```bash
$ profiler list
Basic events:
  cpu
  alloc
  lock
  wall
  itimer
Perf events:
  page-faults
  context-switches
  cycles
  instructions
  cache-references
  cache-misses
  branches
  branch-misses
  bus-cycles
  L1-dcache-load-misses
  LLC-load-misses
  dTLB-load-misses
  mem:breakpoint
  trace:tracepoint
```

If you encounter the permissions/configuration issues of the OS itself and then missing some events, you can refer to the [async-profiler](https://github.com/jvm-profiling-tools/async-profiler) documentation.

You can use the `--event`{{}} parameter to specify the event to sample, such as sampling the `alloc`{{}} event:

`profiler start --event alloc`{{execute T2}}

### Resume sampling

`profiler resume`{{execute T2}}

The difference between `start`{{}} and `resume`{{}} is: `start`{{}} is the new start sampling, `resume`{{}} will retain the data of the last `stop`{{}} .

You can verify the number of samples by executing `profiler getSamples`{{}} .

### Use `execute`{{}} action to execute complex commands

`profiler execute 'start,framebuf=5000000'`{{execute T2}}

For example, start sampling:

`profiler execute 'start,framebuf=5000000'`{{execute T2}}

Stop sampling and save to the specified file:

`profiler execute 'stop,file=/root/arthas-output/result.html'`{{execute T2}}

Specific format reference: [arguments.cpp](https://github.com/jvm-profiling-tools/async-profiler/blob/v2.5/src/arguments.cpp#L50)