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> Generate a flame graph using [async-profiler](https://github.com/jvm-profiling-tools/async-profiler)
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The `profiler` command supports generate flame graph for application hotspots.
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The basic usage of the `profiler` command is `profiler action [actionArg]`
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### Supported Options
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|Name|Specification|
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|---:|:---|
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|*action*|Action to execute|
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|*actionArg*|Attribute name pattern|
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|[i:]|sampling interval in ns (default: 10'000'000, i.e. 10 ms)|
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|[f:]|dump output to specified directory|
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|[d:]|run profiling for specified seconds|
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|[e:]|which event to trace (cpu, alloc, lock, cache-misses etc.), default value is cpu|
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### View all supported actions
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`profiler actions`{{execute T2}}
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```bash
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$ profiler actions
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Supported Actions: [resume, dumpCollapsed, getSamples, start, list, execute, version, stop, load, dumpFlat, actions, dumpTraces, status]
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```
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### View version
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`profiler version`{{execute T2}}
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```bash
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$ profiler version
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Async-profiler 1.6 built on Sep 9 2019
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Copyright 2019 Andrei Pangin
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```
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### Start profiler
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`profiler start -e itimer`{{execute T2}}
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```
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$ profiler start
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Started [cpu] profiling
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```
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> By default, the sample event is `cpu`. Can be specified with the `--event` parameter.
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> Since katacoda environment doesn't support `perf_events`，here use `-e itimer` to specify event to be `itimer`
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### Get the number of samples collected
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`profiler getSamples`{{execute T2}}
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```
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$ profiler getSamples
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23
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```
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### View profiler status
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`profiler status`{{execute T2}}
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```bash
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$ profiler status
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[cpu] profiling is running for 4 seconds
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```
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Can view which `event` and sampling time.
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### Stop profiler
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#### Generate svg format results
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`profiler stop`{{execute T2}}
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```
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$ profiler stop
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profiler output file: /tmp/demo/arthas-output/20191125-135546.svg
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OK
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```
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By default, the generated results are saved to the `arthas-output` directory under the application's `working directory`. The output result path can be specified by the `--file` parameter. such as:
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`profiler stop --file /tmp/output.svg`{{execute T2}}
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```bash
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$ profiler stop --file /tmp/output.svg
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profiler output file: /tmp/output.svg
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OK
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```
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#### Generating html format results
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By default, the result file is `svg` format. If you want to generate the `html` format, you can specify it with the `--format` parameter:
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`profiler stop --format html`{{execute T2}}
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```bash
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$ profiler stop --format html
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profiler output file: /tmp/test/arthas-output/20191125-143329.html
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OK
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```
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Or use the file name name format in the `--file` parameter. For example, `--file /tmp/result.html`.
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`profiler stop --file /tmp/result.html`{{execute T2}}
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### View profiler results under arthas-output via browser
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By default, arthas uses http port 8563, which can be opened: https://[[HOST_SUBDOMAIN]]-8563-[[KATACODA_HOST]].environments.katacoda.com/arthas-output/ View the `arthas-output` directory below Profiler results:
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Click to view specific results:
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> If using the chrome browser, may need to be refreshed multiple times.
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### Profiler supported events
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`profiler list`{{execute T2}}
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Under different platforms and different OSs, the supported events are different. For example, under macos:
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```bash
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$ profiler list
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Basic events:
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cpu
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alloc
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lock
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wall
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itimer
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```
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Under linux
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```bash
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$ profiler list
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Basic events:
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cpu
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alloc
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lock
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wall
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itimer
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Perf events:
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page-faults
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context-switches
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cycles
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instructions
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cache-references
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cache-misses
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branches
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branch-misses
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bus-cycles
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L1-dcache-load-misses
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LLC-load-misses
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dTLB-load-misses
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mem:breakpoint
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trace:tracepoint
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```
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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.
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You can use the `--event` parameter to specify the event to sample, such as sampling the `alloc` event:
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`profiler start --event alloc`{{execute T2}}
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```bash
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$ profiler start --event alloc
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```
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### Resume sampling
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|
`profiler resume`{{execute T2}}
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```bash
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|
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$ profiler resume
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|
Started [cpu] profiling
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```
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The difference between `start` and `resume` is: `start` is the new start sampling, `resume` will retain the data of the last `stop`.
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You can verify the number of samples by executing `profiler getSamples`.
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### Use `execute` action to execute complex commands
|
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|
|
`profiler execute 'start,framebuf=5000000'`{{execute T2}}
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For example, start sampling:
|
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|
```bash
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|
|
profiler execute 'start,framebuf=5000000'
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|
|
```
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|
Stop sampling and save to the specified file:
|
|
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|
|
|
`profiler execute 'stop,file=/tmp/result.svg'`{{execute T2}}
|
|
|
|
|
|
```bash
|
|
|
profiler execute 'stop,file=/tmp/result.svg'
|
|
|
```
|
|
|
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|
|
Specific format reference: [arguments.cpp](https://github.com/jvm-profiling-tools/async-profiler/blob/v1.8.1/src/arguments.cpp#L50)
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