.. SPDX-License-Identifier: CC-BY-SA-2.0-UK

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Yocto Project Profiling and Tracing Manual
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Introduction
============

Yocto bundles a number of tracing and profiling tools - this 'HOWTO'
describes their basic usage and shows by example how to make use of them
to examine application and system behavior.

The tools presented are for the most part completely open-ended and have
quite good and/or extensive documentation of their own which can be used
to solve just about any problem you might come across in Linux. Each
section that describes a particular tool has links to that tool's
documentation and website.

The purpose of this 'HOWTO' is to present a set of common and generally
useful tracing and profiling idioms along with their application (as
appropriate) to each tool, in the context of a general-purpose
'drill-down' methodology that can be applied to solving a large number
(90%?) of problems. For help with more advanced usages and problems,
please see the documentation and/or websites listed for each tool.

The final section of this 'HOWTO' is a collection of real-world examples
which we'll be continually adding to as we solve more problems using the
tools - feel free to add your own examples to the list!

General Setup
=============

Most of the tools are available only in 'sdk' images or in images built
after adding 'tools-profile' to your local.conf. So, in order to be able
to access all of the tools described here, please first build and boot
an 'sdk' image e.g. ::

   $ bitbake core-image-sato-sdk

or alternatively by adding 'tools-profile' to the EXTRA_IMAGE_FEATURES line in
your local.conf::

   EXTRA_IMAGE_FEATURES = "debug-tweaks tools-profile"

If you use the 'tools-profile' method, you don't need to build an sdk image -
the tracing and profiling tools will be included in non-sdk images as well e.g.::

   $ bitbake core-image-sato

.. note::

   By default, the Yocto build system strips symbols from the binaries
   it packages, which makes it difficult to use some of the tools.

   You can prevent that by setting the
   :term:`INHIBIT_PACKAGE_STRIP`
   variable to "1" in your ``local.conf`` when you build the image::

      INHIBIT_PACKAGE_STRIP = "1"

   The above setting will noticeably increase the size of your image.

If you've already built a stripped image, you can generate debug
packages (xxx-dbg) which you can manually install as needed.

To generate debug info for packages, you can add dbg-pkgs to
EXTRA_IMAGE_FEATURES in local.conf. For example::

   EXTRA_IMAGE_FEATURES = "debug-tweaks tools-profile dbg-pkgs"

Additionally, in order to generate the right type of debuginfo, we also need to
set :term:`PACKAGE_DEBUG_SPLIT_STYLE` in the ``local.conf`` file::

   PACKAGE_DEBUG_SPLIT_STYLE = 'debug-file-directory'