arthas/tutorials/katacoda/command-profiler-en/profiler.md

Generate a flame graph using async-profiler

The profiler command supports generate flame graph for application hotspots.

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

Supported Options

Name	Specification
action	Action to execute
actionArg	Attribute name pattern
[i:]	sampling interval in ns (default: 10'000'000, i.e. 10 ms)
[f:]	dump output to specified directory
[d:]	run profiling for specified seconds
[e:]	which event to trace (cpu, alloc, lock, cache-misses etc.), default value is cpu

View all supported actions

profiler actions{{execute T2}}

$ profiler actions
Supported Actions: [resume, dumpCollapsed, getSamples, start, list, execute, version, stop, load, dumpFlat, actions, dumpTraces, status]

View version

profiler version{{execute T2}}

$ profiler version
Async-profiler 1.6 built on Sep  9 2019
Copyright 2019 Andrei Pangin

Start profiler

profiler start -e itimer{{execute T2}}

$ profiler start
Started [cpu] profiling

By default, the sample event is cpu. Can be specified with the --event parameter. Since katacoda environment doesn't support perf_events，here use -e itimer to specify event to be itimer

Get the number of samples collected

profiler getSamples{{execute T2}}

$ profiler getSamples
23

View profiler status

profiler status{{execute T2}}

$ profiler status
[cpu] profiling is running for 4 seconds

Can view which event and sampling time.

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}}

$ profiler stop --format html
profiler output file: /tmp/test/arthas-output/20211207-111550.html
OK

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

profiler stop --file /tmp/result.html{{execute T2}}

View profiler results under arthas-output via browser

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:

Click to view specific results:

If using the chrome browser, may need to be refreshed multiple times.

Profiler supported events

profiler list{{execute T2}}

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

$ profiler list
Basic events:
  cpu
  alloc
  lock
  wall
  itimer

Under linux

$ 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 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}}

$ profiler start --event alloc

Resume sampling

profiler resume{{execute T2}}

$ profiler resume
Started [cpu] profiling

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'

Stop sampling and save to the specified file:

profiler execute 'stop,file=/tmp/result.html'{{execute T2}}

profiler execute 'stop,file=/tmp/result.html'

Specific format reference: arguments.cpp