Austin 3: 0-instrumentation, 0-impact Python CPU/wall time and memory profiling
GitHub - P403n1x87/austin: Python frame stack sampler for CPython

A Frame Stack Sampler for CPython

  
      
  
      
  


  
  
  
  
  
  
  
  
  
  
  
  


  
    
  


  Synopsis •
  Installation •
  Usage •
  Cheat sheet •
  Compatibility •
  Why  Austin •
  Examples •
  Contribute


  
    
  


This is the nicest profiler I’ve found for Python. It’s
cross-platform, doesn’t need me to change the code that’s being profiled, and
its output can be piped directly into flamegraph.pl. I just used it
to pinpoint a gross misuse of SQLAlchemy at work that’s run in some code at the
end of each day, and now I can go home earlier.-- gthm on lobste.rs
If people are looking for a profiler, Austin looks pretty
cool. Check it out!-- Michael Kennedy on Python Bytes 180
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Synopsis
Austin is a Python frame stack sampler for CPython written in pure C. Samples
are collected by reading the CPython interpreter virtual memory space to
retrieve information about the currently running threads along with the stack of
the frames that are being executed. Hence, one can use Austin to easily make
powerful statistical profilers that have minimal impact on the target
application and that don't require any instrumentation.
The key features of Austin are:

Zero instrumentation;
Minimal impact;
Fast and lightweight;
Time and memory profiling;
Built-in support for multi-process applications (e.g. mod_wsgi).

The simplest way to turn Austin into a full-fledged profiler is to use together
with the VS
Code
extension or combine it with FlameGraph or Speedscope. However, Austin's
simple output format can be piped into any other external or custom tool for
further processing. Look, for instance, at the following Python TUI

  

Check out A Survey of Open-Source Python
Profilers
by Peter Norton for a general overview of Austin.
Keep reading for more tool ideas and examples!

💜Austin is a free and open-source project. A lot of
effort goes into its development to ensure the best performance and that it
stays up-to-date with the latest Python releases. If you find it useful,
consider sponsoring this
project.🙏

Installation
Austin is available to install from PyPI and from the major software
repositories of the most popular platforms. Check out the latest release page
for pre-compiled binaries and installation packages.
On all supported platforms and architectures, Austin can be installed from PyPI
with pip or pipx via the commands

or

On Linux, it can be installed using autotools or as a snap from the Snap
Store. The latter will automatically perform the
steps of the autotools method with a single command. On distributions derived
from Debian, Austin can be installed from the official repositories with
apt. Anaconda users can install Austin from Conda Forge.
On Windows, Austin can be easily installed from the command line using either
Chocolatey or Scoop. Alternatively, you can download the installer from the
latest release page.
On macOS, Austin can be easily installed from the command line using Homebrew.
Anaconda users can install Austin from Conda Forge.
For any other platforms, compiling Austin from sources is as easy as cloning the
repository and running the C compiler. The Releases page has many
pre-compiled binaries that are ready to be uncompressed and used.
With autotools
Installing Austin using autotools amounts to the usual ./configure, make
and make install finger gymnastic. The only dependency is the standard C
library. Before proceeding with the steps below, make sure that the autotools
are installed on your system. Refer to your distro's documentation for details
on how to do so.
git clone --depth=1 https://github.com/P403n1x87/austin.git && cd austin
autoreconf --install
./configure
make
make install

NOTE Some Linux distributions, like Manjaro, might require the execution
of automake --add-missing before ./configure.

Alternatively, sources can be compiled with just a C compiler (see below).
From the Snap Store
Austin can be installed on many major Linux
distributions from the Snap Store
with the following command
sudo snap install austin --classic
On Debian and Derivatives
On March 30 2019 Austin was accepted into the official Debian repositories and
can therefore be installed with the apt utility.
sudo apt update -y && sudo apt install austin -y
On macOS
Austin can be installed on macOS using Homebrew:

From Chocolatey
To install Austin from Chocolatey, run
the following command from the command line or from PowerShell

To upgrade run the following command from the command line or from PowerShell:

From Scoop
To install Austin using Scoop, run the following command from the command line
or PowerShell

To upgrade run the following command from the command line or PowerShell:

From Conda Forge
Anaconda users on Linux and macOS can install Austin from Conda Forge with the
command
conda install -c conda-forge austin
From Sources without autotools
To install Austin from sources using the GNU C compiler, without autotools,
clone the repository with
git clone --depth=1 https://github.com/P403n1x87/austin.git
On Linux, one can then use the command
gcc -O3 -Os -Wall -pthread src/*.c -o src/austin
whereas on macOS it is enough to run
gcc -O3 -Os -Wall src/*.c -o src/austin
On Windows, the -lpsapi -lntdll switches are needed
gcc -O3 -Os -Wall -lpsapi -lntdll src/*.c -o src/austin
Add -DDEBUG if you need a more verbose log. This is useful if you encounter a
bug with Austin and you want to report it here.
Usage

Usage: austin [OPTION...] command [ARG...]
Austin is a frame stack sampler for CPython that is used to extract profiling
data out of a running Python process (and all its children, if required) that
requires no instrumentation and has practically no impact on the tracee.

  -b, --binary               Emit data in the MOJO binary format. See
                             https://github.com/P403n1x87/austin/wiki/The-MOJO-file-format
                             for more details.
  -C, --children             Attach to child processes.
  -f, --full                 Produce the full set of metrics (time +mem -mem).
  -g, --gc                   Sample the garbage collector state.
  -h, --heap=n_mb            Maximum heap size to allocate to increase sampling
                             accuracy, in MB (default is 0).
  -i, --interval=n_us        Sampling interval in microseconds (default is
                             100). Accepted units: s, ms, us.
  -m, --memory               Profile memory usage.
  -o, --output=FILE          Specify an output file for the collected samples.
  -p, --pid=PID              Attach to the process with the given PID.
  -P, --pipe                 Pipe mode. Use when piping Austin output.
  -s, --sleepless            Suppress idle samples to estimate CPU time.
  -t, --timeout=n_ms         Start up wait time in milliseconds (default is
                             100). Accepted units: s, ms.
  -w, --where=PID            Dump the stacks of all the threads within the
                             process with the given PID.
  -x, --exposure=n_sec       Sample for n_sec seconds only.
  -?, --help                 Give this help list
      --usage                Give a short usage message
  -V, --version              Print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

Report bugs to <https://github.com/P403n1x87/austin/issues>.


The output is a sequence of frame stack samples, one on each line. The format is
the collapsed one that is recognised by FlameGraph so that it can be piped
straight to flamegraph.pl for a quick visualisation, or redirected to a file
for some further processing.
By default, each line has the following structure:
P<pid>;T<iid>:<tid>[;[frame]]* [metric]*

where the structure of [frame] and the number and type of metrics on each line
depend on the mode. The <pid>, <iid> and <tid> component represent the
process ID, the sub-interpreter ID, and the thread ID respectively.
Environment variables
Some behaviour of Austin can be configured via environment variables.



Variable
Effect




AUSTIN_NO_LOGGING
Disables all log messages (since Austin 3.4.0).



Normal Mode
In normal mode, the [frame] part of each emitted sample has the structure
[frame] := <module>:<function>:<line number>

Each line then ends with a single [metric], i.e. the sampling time measured in
microseconds.

NOTE This was changed in Austin 3. In previous version, the alternative
format used to be the default one.

Binary Mode
The output generated by Austin by default can be quickly visualised by some
existing tools without further processing. However, this comes at the cost of
potentially big raw output files. The binary mode can be used to produce a more
compact binary representation of the collected data, and more efficiently, by
exploiting the performance enhancement of internal caching of frame data.
The mojo2austin CLI tool that comes with the austin-python Python package
can be used to convert a MOJO file back to the standard Austin output. Be aware
that the resulting file might be quite large, well over 4 times the size of the
MOJO file itself.
More details about the MOJO binary format can be found in the Wiki.
Since Austin 3.4.0.
Column-level Location Information
Since Python 3.11, code objects carry finer-grained location information at the
column level. When using the binary MOJO format, Austin can extract this extra
location information when profiling code running with versions of the
interpreter that expose this data.
Since Austin 3.5.0.
Memory and Full Metrics
When profiling in memory mode with the -m or --memory switch, the metric
value at the end of each line is the memory delta between samples, measured in
bytes. In full mode (-f or --full switches), each sample ends with a
comma-separated list of three values: the time delta, the idle state (1 for
idle, 0 otherwise) and the RSS memory delta (positive for memory allocations,
negative for deallocations). This way it is possible to estimate wall-clock
time, CPU time and memory pressure, all from a single run.

NOTE The reported memory allocations and deallocations are obtained by
computing resident memory deltas between samples. Hence these values give an
idea of how much physical memory is being requested/released.

Multi-process Applications
Austin can be told to profile multi-process applications with the -C or
--children switch. This way Austin will look for new children of the parent
process.
Sub-interpreters
Austin has support for Python applications that make use of sub-interpreters.
This means that Austin will sample all the sub-interpreters that are running
within each process making up the Python application.
Since Austin 3.6.0.
Garbage Collector Sampling
Austin can sample the Python garbage collector state for applications running
with Python 3.7 and later versions. If the -g/--gc option is passed, Austin
will append :GC: at the end of each collected frame stack whenever the garbage
collector is collecting. This gives you a measure of how busy the Python GC is
during a run.
Since Austin 3.1.0.
Where?
If you are only interested in what is currently happening inside a Python
process, you can have a quick overview printed on the terminal with the
-w/--where option. This takes the PID of the process whose threads you want to
inspect, e.g.
sudo austin -w `pgrep -f my-running-python-app`
Below is an example of what the output looks like

  

This works with the -C/--children option too. The emojis to the left indicate
whether the thread is active or sleeping and whether the process is a child or
not.
Since Austin 3.3.0.
Sampling Accuracy
Austin tries to keep perturbations to the tracee at a minimum. To do so, the
tracee is never halted. To improve sampling accuracy, Austin can allocate a heap
that is used to get large snapshots of the private VM of the tracee that is
likely to contain frame information in a single attempt. The larger the heap is
allowed the grow, the more accurate the results. The maximum size of the heap
that Austin is allowed to allocate can be controlled with the -h/--heap
option, followed by the maximum size in bytes. By default, Austin does not
allocate a heap, which is ideal for systems with limited resources. If you think
your results are not accurate, try setting this parameter.
Since Austin 3.2.0.
Changed in Austin 3.3.0: the default heap size is 0.
Native Frame Stack
If you want observability into the native frame stacks, you can use the
austinp variant of austin which can be obtained by compiling the source
with -DAUSTINP on Linux, or from the released binaries.
austinp makes use of ptrace to halt the application and grab a
snapshot of the call stack with libunwind. If you are compiling austinp from
sources make sure that you have the development version of the libunwind
library available on your system, for example on Ubuntu,
sudo apt install libunwind-dev binutils-dev
and compile with
gcc -O3 -Os -Wall -pthread src/*.c -DAUSTINP -lunwind-ptrace -lunwind-generic -lbfd -o src/austinp
then use as per normal. The extra -k/--kernel option is available with
austinp which allows sampling kernel call stacks as well.

WARNING Since austinp uses ptrace, the impact on the tracee is no
longer minimal and it becomes higher at smaller sampling intervals. Therefore
the use of austinp is not recommended in production environments. For this
reason, the default sampling interval for austinp is 10 milliseconds.

The austinp-resolve tool from the austin-python Python package can be used
to resolve the VM addresses to source and line numbers, provided that the
referenced binaries have DWARF debug symbols. Internally, the tool uses
addr2line(1) to determine the source name and line number given an address,
when possible.

Whilst austinp comes with a stripped-down implementation of addr2line, it
is only used for the "where" option, as resolving symbols at runtime is
expensive. This is to minimise the impact of austinp on the tracee, increase
accuracy and maximise the sampling rate.

The where option is also available for the austinp variant and will
show both native and Python frames. Highlighting helps tell frames apart. The
-k option outputs Linux kernel frames too, as shown in this example

  


NOTE If you have installed Austin from the Snap Store, the austinp
executable will be available as austin.p from the command line.

Logging
Austin uses syslog on Linux and macOS, and %TEMP%\austin.log on Windows
for log messages, so make sure to watch these to get execution details and
statistics. Bad frames are output together with the other frames. In general,
entries for bad frames will not be visible in a flame graph as all tests show
error rates below 1% on average.
Logging can be disabled using environment variables.
Cheat sheet
All the above Austin options and arguments are summarised in a cheat sheet that
you can find in the doc
folder in either the SVG, PDF or PNG format

  

Compatibility
Austin supports Python 3.8 through 3.13, and has been tested on the following
platforms and architectures











x86_64
✓
✓
✓


i686
✓

✓


armv7
✓




arm64
✓

✓


ppc64le
✓






NOTE Austin might work with other versions of Python on all the
platforms and architectures above. So it is worth giving it a try even if
your system is not listed below. If you are looking for support for Python <
3.8, you can use Austin 3.5.

Because of platform-specific details, Austin usage may vary slightly. Below are
further compatibility details to be aware of.
On Linux
Austin requires the CAP_SYS_PTRACE capability to attach to an external
process. This means that you will have to either use sudo when attaching to
a running Python process or grant the CAP_SYS_PTRACE capability to the Austin
binary with, e.g.
sudo setcap cap_sys_ptrace+ep `which austin`
To use Austin with Docker, the --cap-add SYS_PTRACE option needs to be passed
when starting a container.
On MacOS
Due to the System Integrity Protection, introduced in MacOS with El
Capitan, and the Hardened Runtime, introduced in Mojave,
Austin cannot profile Python processes that use an executable located in the
/bin folder, or code-signed, even with sudo. This is the case for the
system-provided version of Python, and the one installed with the official
installers from python.org. Other installation methods,
like pyenv or Anaconda or
Homebrew are known to work with
Austin, out of the box.
To use Austin with Python from the official installer, you could remove the
signature from the binaries with
codesign --remove-signature /Library/Frameworks/Python.framework/Versions/<M.m>/bin/python3
codesign --remove-signature /Library/Frameworks/Python.framework/Versions/<M.m>/Resources/Python.app/Contents/MacOS/Python
Alternatively, you could self-sign the Austin binary with the Debugging Tool
Entitlement, as done for debugging tools like GDB. However, this method
has not been tested.

Austin requires the use of sudo to work on MacOS. To avoid having to type
the password every time you use Austin, consider adding a rule to the
sudoers file, e.g.
yourusername  ALL = (root) NOPASSWD: /usr/local/bin/austin


Why Austin
When there already are similar tools out there, it's normal to wonder why one
should be interested in yet another one. So here is a list of features that
currently distinguish Austin.


Written in pure C Austin is written in pure C code. There are no
dependencies on third-party libraries except for the standard C library and
the API provided by the Operating System.


Just a sampler Austin is just a frame stack sampler. It looks into a
running Python application at regular intervals of time and dumps whatever
frame stack it finds. The samples can then be analysed at a later time so that
Austin can sample at rates higher than other non-C alternatives that perform
some aggregations at run-time.


Simple output, powerful tools Austin uses the collapsed stack format of
FlameGraph that is easy to parse. You can then go and build your own tool to
analyse Austin's output. You could even make a player that replays the
application execution in slow motion, so that you can see what has happened in
temporal order.


Small size Austin compiles to a single binary executable of just a bunch
of KB.


Easy to maintain Occasionally, the Python C API changes and Austin will
need to be adjusted to new releases. However, given that Austin, like CPython,
is written in C, implementing the new changes is rather straight-forward.


Examples
The following flame graph has been obtained with the command
austin -i 1ms ./test.py | sed '/^#/d' | ./flamegraph.pl --countname=μs > test.svg
where the sample test.py script has the execute permission and the following
content
#!/usr/bin/env python3

import dis

for i in range(1000):
    dis.dis(dis.dis)

  

To profile Apache2 WSGI application, one can attach Austin to the web server
with
austin -Cp `pgrep apache2 | head -n 1`
Any child processes will be automatically detected as they are created and
Austin will sample them too.
IDE Extensions
It is easy to write your own extension for your favourite text editor. This, for
example, is a demo of a Visual Studio Code extension that highlights the most
hit lines of code straight into the editor

  

Austin TUI
The Austin TUI is a text-based user interface for Austin that gives you a
top-like view of what is currently running inside a Python application. It is
most useful for scripts that have long-running procedures as you can see where
execution is at without tracing instructions in your code. You can also save the
collected data from within the TUI and feed it to Flame Graph for visualisation,
or convert it to the pprof format.
If you want to give it a go you can install it using pip with
pip install austin-tui --upgrade
and run it with
austin-tui [OPTION...] command [ARG...]
with the same command line as Austin. Please note that the austin binary
should be available from within the PATH environment variable in order for the
TUI to work.

The TUI is based on python-curses. The version included with the standard
Windows installations of Python is broken so it won't work out of the box. A
solution is to install the wheel of the port to Windows from
this page. Wheel files
can be installed directly with pip, as described in the
linked
page.



  

Austin Web
Austin Web is a web application that wraps around Austin. At its core, Austin
Web is based on d3-flame-graph to display a live flame graph in the browser,
that refreshes every 3 seconds with newly collected samples. Austin Web can also
be used for remote profiling by setting the --host and --port options.
If you want to give it a go you can install it using pip with
pip install austin-web --upgrade
and run it with
austin-web [OPTION...] command [ARG...]
with the same command line as Austin. This starts a simple HTTP server that
serves on localhost by default. When no explicit port is given, Austin Web
will use an ephemeral one.
Please note that the austin binary should be available from within the PATH
environment variable in order for Austin Web to work.

  

Speedscope
Austin output is now supported by Speedscope. However, the austin-python
library comes with format conversion tools that allow converting the output from
Austin to the Speedscope JSON format.
If you want to give it a go you can install it using pip with
pip install austin-python --upgrade
and run it with
austin2speedscope [-h] [--indent INDENT] [-V] input output
where input is a file containing the output from Austin and output is the
name of the JSON file to use to save the result of the conversion, ready to be
used on Speedscope.

  

Google pprof
Austin's format can also be converted to the Google pprof format using the
austin2pprof utility that comes with austin-python. If you want to give it
a go you can install it using pip with
pip install austin-python --upgrade
and run it with
austin2pprof [-h] [-V] input output
where input is a file containing the output from Austin and output is the
name of the protobuf file to use to save the result of the conversion, ready to
be used with Google's pprof tools.
Contribute
If you like Austin and you find it useful, there are ways for you to contribute.
If you want to help with the development, then have a look at the open issues
and have a look at the contributing guidelines before you
open a pull request.
You can also contribute to the development of the Austin by becoming a sponsor
and/or by buying me a coffee on BMC or
by chipping in a few pennies on PayPal.Me.

  
  
  



  
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