Chapter 7. GProf Profile Plugin Support

The Linux Tools GProf plugin brings the profiling capabilities of the GNU profiler, gprof, to Eclipse, in a manner that is easy to use by developers with different levels of experience. eCos and eCosPro have the ability to generate the data used in the generation of gprof profile timing and call graphs (for additional information, please refer to the Profiling section of the eCos and eCosPro Reference Manual). The eCosPro CDT plug-in includes functionality to extract the data from an eCosPro application that is running, or has been halted on the target hardware, through the Eclipse GUI and provides as input this data to the Linux Tools GProf plugin.

This section describes how to bring all the above functionality together to permit you to graphically view and explore the target hardware application's profile and timing data on your development host. This will allow you to analyse and explore your code within the Eclipse GUI to determine not only the parts of your application which are slower in execution than expected, but also can help you find many other statistics through which potential bugs can discovered and resolved. This section also provides a walk-through of the installation of the Linux Tools GProf plugin, the configuration of eCosPro and creation and compilation of the eCosPro C/C++ Application Project such that profiling data is generated, through to the capture and display of the profiling data.

[Note]Note

GProf Profile support is not available on all target platforms. It requires an implementation of the profiling timer, there should be a hardware- specific implementation of mcount and it is not currently available for multi-core (SMP) systems. For further details, please refer to the Profiling documentation and the target-specific eCosPro documentation.

7.1. GProf Profile Plugin Installation

The current Eclipse distribution provided with the eCosPro Developer's Kit version 4.x and above includes the Linux Tools GProf plugin pre-installed. If you are using an earlier version of Eclipse or a distribution from a different source, you can follow the instructions in this section to install the Linux Tools GProf plugin.

7.1.1. Check if Linux Tools GProf plugin is installed

To check whether the Linux Tools GProf plugin is installed, within Eclipse select from the menu HelpAbout Eclipse and press the Installation Details button. Within the resulting dialog illustrated in Figure 7.1, “Eclipse Installation Details - GProf” look in the Configuration contents: section for “GProf Integration”. If present, the plugin is installed.

Figure 7.1. Eclipse Installation Details - GProf

Eclipse Installation Details - GProf

7.1.2. Install Linux Tools GProf plugin

To install the Linux Tools GProf plugin is installed you will need internet access. Within Eclipse select from the menu HelpInstall New Software and within the Work with: field of the resulting dialog, enter the name of your Eclipse Installation and choose the download URL. An example illustration of the dialog is shown in Figure 7.2, “Eclipse Install GProf”. For example, “Oxygen - http://download.eclipse.org/releases/oxygen”.

Figure 7.2. Eclipse Install GProf

Eclipse Install GProf

Select Performance, Profiling and Tracing ToolsGProf Integration and ensure the latter is checked. Select the Next button to confirm the install details followed by Next to confirm your acceptance of the license terms by selecting I accept the terms of the license agreement. Select the Finish button to confirm agreement and begin the installation process. On completion of the installation you will be required to restart Eclipse.

7.2. The eCosPro Runtime profile statistics package

Runtime support is required from the operating system in order to create and store the profiling data on the target platform and may easily be added by including the Application profile support package, also known as CYGPKG_PROFILE_GPROF, into your eCos configuration. This may be achieved through one of two methods:

7.2.1. Adding CYGPKG_PROFILE_GPROF with the eCos Configuration Tool

Open up your eCos configuration within the eCos Configuration Tool and select BuildPackages (Ctrl+P) and type gprof into the Keywords field as illustrated in Figure 7.3, “Configuration Tool Install GProf Package”.

Figure 7.3. Configuration Tool Install GProf Package

Configuration Tool Install GProf Package

If already installed, the package Application profile support will appear in the right-hand column under Use these packages. If not installed, it will appear under the Available Packages column. In this case select the Add button to move the package to the right-hand column followed by selecting the OK button to accept the addition of the package. Finally select FileSave (Ctrl+S) to save your configuration followed optionally by BuildLibrary (F7) to rebuild the eCos library. The latter step is optional as Eclipse will rebuild the library as soon as you exit the eCos Configuration Tool if it detects a change in the active configuration file.

7.2.2. Adding CYGPKG_PROFILE_GPROF with the command line

Open a command shell with the appropriate environment variables set and, assuming your eCos configuration is named ecos.ecc, the commands illustrated in Example 7.1, “Adding CYGPKG_PROFILE_GPROF with the command line” will add the CYGPKG_PROFILE_GPROF package and rebuild the eCos library.

Example 7.1. Adding CYGPKG_PROFILE_GPROF with the command line

$ ecosconfig add CYGPKG_PROFILE_GPROF 
$ ecosconfig tree
$ make

7.2.3. Enabling TFTP support for profiling data extraction

Normally the capture of profiling data from the target platform requires the temporary suspension of all code execution on the target platform while the data is extracted, either through the use of a GDB monitor or a hardware debugger.

However, if your eCos Configuration includes the FredBSD networking stack (the CYGPKG_NET_FREEBSD_STACK package) with the TFTP server option enabled (the default), the profiling data may be extracted from the target platform without temporarily suspending all code execution. This is achieved through the use of an additional low- priority eCos thread that provides a TFTP service (on port 69, the default) which allows the transfer of the profiling data from the target hardware to occur over TFTP. The eCos CYGPKG_PROFILE_GPROF package by default creates this thread when the CYGPKG_NET_FREEBSD_STACK package is enabled.

When capturing profiling data in this manner, the eCosPro CDT plug-in needs to be configured where the profiling data will be captured from, otherwise the default method through GDB is used. Open the debug launch configuration window you previously created to launch the binary in Section 4.1, “eCos Launch Configurations” and select the Profiling tab. This dialog is illustrated in Figure 7.4, “Profiling Data Capture through TFTP”.

Figure 7.4. Profiling Data Capture through TFTP

Profiling Data Capture through TFTP

Check the Fetch data via TFTP instad of GDB (requires TFTP server on target) field and fill in appropriate values for the Hostname / IP address for the target platform's network address and Port number. The default port number set by the CYGPKG_NET_FREEBSD_STACK package for the TFTP server is 69.

7.3. Enabling profiling data generation within eCos and the eCosPro application

The generation of profiling data does not happen automatically when the CYGPKG_NET_FREEBSD_STACK package is added to eCos. The inclusion of this package within your eCos configuration just enables runtime support. Code has to be compiled with the -pg GNU compiler flag to make it capable of generating profiling data.

7.3.1. Compiling the application with the -pg GNU compiler flag

You may enable this flag project-wide by bringing up the project's properties dialog as described in Section 5.3, “Application Project Properties”, and selecting C/C++ BuildSettings, selecting the Tool Settings tab in the right-hand panel and within tree of settings selecting either eCos gccDebugging or eCos g++Debugging whether you wish profiling data to be generated for either C or C++ code, or both. Check the Generate gprof information (-pg) field from the right-hand panel, apply the changes and close the dialog by pressing the Apply and OK buttons respectively. This is illustrated in Figure 7.5, “Enable Application Profiling Data Generation”.

Figure 7.5. Enable Application Profiling Data Generation

Enable Application Profiling Data Generation

The -pg GNU compiler flag may also be enabled or disabled for individual source files by opening the properties dialog for each source file (similar to opening the application project's properties, but start by highlighting the source file within the Project Explorer window of the C/C++ perspective) and checking or unchecking the Generate gprof information (-pg) field.

7.3.2.  Compiling eCos with the -pg GNU compiler flag

eCos and eCosPro functions may also be included for profiling data generation and analysis. This may be acheived by adding the -pg GNU compiler flag to the value of CYGBLD_GLOBAL_CFLAGS configuration macro. To add or remove the flag, open the eCos configuration in the eCos Configuraion Tool as described in Section 6.2.1, “Editing the eCos configuration project”, and search using the Find in configuration dialog, reached through the menu options EditFind (Ctrl+F) for CYGBLD_GLOBAL_CFLAGS (as Find what) with Search in set to Macro Names. Once visible, left mouse click in the value field (or double-left click to bring up a String Edit dialog) and add or remove the -pg flag to/from the value as required.

Finally select FileSave (Ctrl+S) to save your configuration followed optionally by BuildLibrary (F7) to rebuild the eCos library.

7.4. Enabling and Disabling profiling data collection

Enabling and disabling the collection of profiling data is done programatically by the application through the following two functions: profile_on and profile_off.

7.4.1. Enable profiling data collection

The application must call the function profile_on to start the collection of profiling data. If the TFTP daemon is enabled, the call to profile_on must happen once the network is up and running, typically after the call to init_all_network_interfaces. This is because the TFTP daemon will be started within profile_on.

[Note]Note

profile_on may be invoked multiple times but each invocation will allocate a fresh profiling range, deleting the previous range.

A typical example is illustrated in Example 7.2, “Enable profiling data collection”.

Example 7.2. Enable profiling data collection

#include <pkgconf/system.h>
#ifdef CYGPKG_NET
# include <network.h>
#endif
#ifdef CYGPKG_PROFILE_GPROF
# include <cyg/profile/profile.h>
#endif
…
int
main(int argc, char** argv)
{
    …
#ifdef CYGPKG_NET
    init_all_network_interfaces();
#endif
    …

#ifdef CYGPKG_PROFILE_GPROF
    {
        extern char _stext[], _etext[];
        profile_on(_stext, _etext, 16, 3500);
    }
#endif
    …
}

The profile_on function takes four arguments:

start address, end address

These two arguments specify a range of addresses that are to be profiled in a contiguous section of memory. The eCos linker script export the symbols _stext and _etext on most targets and these correspond to the beginning and end of code. Profiling may be performed on a subset of code by specifying the start and end addresses of the code region on which profiling is to be performed.

bucket size

This is the bucket size which the profile_on divides the range of addresses into. It dynamically allocates a single array of 16-bit counters with one entry for each bucket. When the profiling timer interrupts, the interrupt handler will examine the program counter of the interrupted code and, assuming it is within the range of valid addresses, find the containing bucket and increment the appropriate counter.

[Note]Notes
  • The number of 16-bit counters is determined by the range of addresses being profiled and by the bucket size. Smaller bucket sizes and large memory ranges will require more memory, so if the target hardware is low on memory this may be unacceptable. The memory requirements can be reduced by reducing the code range or increasing the bucket size. The latter increase will affect the accuracy of the results, making gprof more likely to report the wrong function and increasing the risk of a counter overflow.

  • The bucket size must be a power of 2 and will be adjusted if necessary. This is done for the sake of run-time efficiency.

time interval

This specifies, in units of microseconds, the interval between profile timer interrupts. Increasing this value gives more accurate profiling results but will result in higher run-time overheads and a greater risk of a counter overflow. This value may be modified by the implementation because of hardware restrictions, so as a result the generated profile data contains the actual interval used.

[Tip]Tip

Avoid using an interval that is a simple fraction of the system clock, typically 10000 microseconds, as use of such intervals runs the risk that the profiling timer will disproportionally sample code that runs only in response to the system clock.

7.4.2. Disabling profiling data collection

The collection of profiling data may be disabled by the application, using a call to profile_off. This will also reset any existing profile data. The function prototype is illustrated in Example 7.3, “profile_off prototype”.

Example 7.3. profile_off prototype

void profile_off(void);

7.5. Extracting and Clearing the profiling data from the target

Extracting and clearing the profiling data from the target platform is a simple operation with eCosPro and the eCosPro CDT plug-in. When eCosPro is configured and built as described in Section 7.2.1, “Adding CYGPKG_PROFILE_GPROF with the eCos Configuration Tool”, the series of macros required to extract and clear the profiling data from the target platform eCos are installed in a file within the ${eCosInstallDir}/etc directory. When required, these macros are loaded by the eCosPro CDT plug-in into GDB and executed.

Also ensure that you have included the code described in Section 7.4.1, “Enable profiling data collection” into your application, configured the launch profile for TFTP if required as described in Section 7.2.3, “Enabling TFTP support for profiling data extraction”, and start executing and debugging your application in the normal fashion.

Figure 7.6. Capture and Clear Profiling Data

Capture and Clear Profiling Data

7.5.1. Extracting the profiling data from the target

To capture the profiling data, select the application's process or one of the application's threads within the Debug Window of the Debug Perspective, and press the Take Profile Snapshot button called out as 1 in Figure 7.6, “Capture and Clear Profiling Data”.

This will extract the profiling data from the target, pausing and resuming execution if necessary, and save it to a file within the project explorer tree in the same directory as the binary executable. The file will have a .gmon extension with the date and time of the snapshot as the base name, allowing multiple snapshots to be taken and saved at different times.

[Note]Note

If you are using a software monitor (e.g. RedBoot) to debug your application and not a hardware debugger, and if the application is not already paused, the snapshot may not immediately be taken but may be delayed until the software monitor is active (e.g. when performing diagnostics output). This is also dependant on the eCos configuration.

7.5.2. Clearing the profiling data from the target

To clear the profiling data, press the Reset Profile Data button called out as 2 in Figure 7.6, “Capture and Clear Profiling Data” when either the application's process or one of the application's threads within the Debug Window of the Debug Perspective is selected. Similar to the capturing of the data, this will pausie and resume execution of the application if necessary.

7.6. Display the profiling data using the GProf plugin

To display the profiling data in the GProf plugin, double click on the .gmon filename corresponding to the data capture you would like to display, or right click on the filename and select Open or Open withGprof editor. If you have multiple binaries, the popup illustrated in Figure 7.7, “Gmon File Viewer: select binary” will appear prompting you to select the binary used to generate the profiling data. If prompted, select the application binary used to generate the profile data.

Figure 7.7. Gmon File Viewer: select binary

Gmon File Viewer: select binary

Select the gprof tab as illustrated in Figure 7.8, “Gprof tab window”.

Figure 7.8. Gprof tab window

Gprof tab window

The Gprof view shows how much execution time is consumed by each part of the application and also provides call graph infomation for each function. The buttons available are:

  • “Show/Hide columns” button allows you to select which columns to display.

  • “Export to CSV” button allows you to export the GProv result as a CSV text file.

  • “Sorting” button allows you to choose the columns, their priority and their ordering by which the data is sorted.

  • “Sort samples per file” button displays the GProf result sorted by file.

  • “Sort samples per function” button displays the GProf result sorted by function.

  • “Sort samples per line” button displays the GProf result sorted by line.

  • “Display function call graph” button displays the GProf result as a call graph.

  • “Switch sample/time” button allows you to switch the data between sample and time results.

  • “Create chart” button allows you to create a chart (Bar/Vertical bar/Pie) from the data selected for the data of selected columns.

For further documentation, please refer to the GProf User Guide.