Difference between revisions of "Linux Tools Project/PERF/User Guide"

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= Overview =
 
= Overview =
  

Revision as of 13:39, 13 July 2012

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Contents

Overview

PERF is a performance counters subsystem in Linux. Performance counters are CPU hardware registers that count hardware events such as instructions executed and cache-misses suffered. These counters aid in profiling applications to detect hotspots in the application. PERF provides per task, per CPU and per-workload counters, sampling on top of these and source code event annotation.

The PERF plug-in for Eclipse allows the developer to execute profiles in their applications in a seamlessly way, using quick launch actions and visualizing the results in an user-friendly interface.

Installing

In order for the Perf plug-in for Eclipse to work properly, you need to have the perf tool installed on your system first. Most Linux distributions will likely package this as a package related to the kernel. More information about the perf tool can be found at https://perf.wiki.kernel.org/ .

Once the perf tool is installed, the easiest way to install the Perf plug-in for Eclipse is through the Software Updates and Add-ons menu. For information on how to use this menu, refer to this link.

Launching a Profile

Perf plug-in provides useful profile information in a user-friendly interface, gathering the required information from the Perf command-line tool and hooking it into the Eclipse and CDT's facilities.

During a profile run, the Perf plug-in will start, stop and perform other Perf tasks in the background as needed, while the binary being profiled runs as normal.

One-click launch

The Perf plug-in for Eclipse includes a one-click launch feature which profiles the binary with default options. To use the one-click launch, right click on the project, the binary or in an open editor for a source file belonging to that project. Then, navigate to Profile As and click Profile With Perf to start the launch.

Perf oneclicklaunch.png

Launching a Customized Profile

The Perf plug-in allows you to configure a profile run using several options. These options are exposed via the launch configuration in a user-friendly manner, allowing for a more complex profile.

To customize a profile, right click on the project, the binary or in an open editor for a source file belonging to that project. Then, navigate to Profile As > Profile Configurations... to open the Profile Configurations menu. Refer to the Profiling Configuration section for more information about configuring a profile.

After configuring a profile, click the Profile button to launch the profile.

Profiling Configuration

The Perf plug-in has several options to configure, most of them are mirrors of the configuration options that exists on the binary. For more information about all these options refer to the Perf man pages or https://perf.wiki.kernel.org/ .

Remote Profiling

It is possible to use RSE or RemoteTools to profile a remote project. In Profile Configurations, after creating a configuration in the Profile with Remote Perf option, it is necessary to search for the project binary. The user can copy the C/C++ executable file from the remote server to the local workstation by selecting the Copy C/C++ executable check box. But the default it to profile the executable file specified in the C/C++ executable field. In this case, you need to browse for the binary. The working directory is automatically set to the underlying project directory, but you can modify it if necessary.

Perf maintabremote.png

Perf Options tab

This configuration tab contains runtime options for a profiling with Perf, such as loading a kernel image file or hide unsolved symbols.

Perf optionstab.png

Perf Events tab

On this tab it is possible to set up a customized array of events for the profiling or, if desired, go with the Default Event option which overrides all other settings and run Perf with the default event (cycle counting).

Perf eventstab.png

Perf View

The Perf view is where all the profiling results can be easily read.

Perf view.png

The tree structure displayed above describes one profile of one or more events in the following manner:

  • Icon-oprofile event.gif Events -- the name of the profiling event used by Perf
    • Icon-oprofile session.gif Session -- the name of the session the profile is stored in
      • Icon-oprofile image.gif Image -- the binary being profiled
        • Icon-oprofile symbol.gif Symbol -- symbols gathered from the binary's debug information
          • Icon-oprofile sample.gif Sample -- individual Perf samples correlated to line numbers of source code
        • Icon-oprofile dependent.gif Dependent Images -- other binaries related to the run of the program; shared libraries or kernel modules
          • Icon-oprofile image.gif Image -- the dependent binary
            • Icon-oprofile symbol.gif Symbol -- same as above
              • Icon-oprofile sample.gif Sample -- same as above