Regression Tests

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See also NewRegressionFramework.

Running Regressions

Running the M5 regression tests is the recommended way to make sure that any changes to the simulator still comply with M5. Regression Testing is performed using SCons to help guide which tests are run. All current tests are located in the: tests/ directory. The command for running regression tests has the following format:

% scons build/<arch>/tests/<binary_type>/<test_directory>/<mode>/<test directory>/<ISA>/linux/<config script>

Here is an example of running all of the 'quick' regression tests for the ALPHA architecture in syscall-emulation (SE) mode. You can leave out any of the trailing details in the directory string to execute all of the sub-tests.

% scons build/ALPHA/tests/debug/quick/se
**** build/ALPHA/tests/debug/quick/se/00.hello/alpha/linux/o3-timing PASSED!
**** build/ALPHA/tests/debug/quick/se/00.hello/alpha/linux/simple-atomic PASSED!
**** build/ALPHA/tests/debug/quick/se/00.hello/alpha/linux/simple-timing PASSED!
**** build/ALPHA/tests/debug/quick/se/00.hello/alpha/tru64/o3-timing PASSED!

The script util/regress can be used for running regression tests. Run the script with the option '-h' or '--help' for the options can be passed to the script. This scripts executes both compiling (scons build/<build_opts (ISA)>/gem5.<compile-variants (opt,debug,etc.)>) and running regressions (scons build/<ISA or build_opts>/tests/<test-variants (opt,debug,etc.)>/<quick/long>/<modes (se/fs)>

The options contained in the test directory passed to scons are detailed below.

  • <arch>: The build to run. This can be any file in gem5/build_opts
  • <binary_type>: The binary to run (e.g., opt, debug)
  • <test_directory>: "quick" or "long" see tests/
  • <mode>: se or fs
  • <test directory>: The directory in tests/<quick or long>/<se or fs> of the test to run. This usually specifies the workload to run (e.g., 00.hello)
  • <ISA>: Lowercase version of ISA to use
  • <config script>: Script from tests/configs to run

Regression scripts execution description

The regression scripts are complicated. Below, we describe the interaction and execution order of all of the scripts.

  1. util/regress executes scons with varying options depending on its parameters.
  2. scons is executed. For compile tests, this is the same way you compile gem5. For regression tests scons executes builds/<build to use>/gem5.<binary name> tests/ <crazy path that encodes everything>
    • Control is now transferred to tests/
    • execute the primary configuration script (the last directory on the scons command line)
    • The way scons knows which tests to run is by looking in tests/<quick or long>/<se or fs>/<secondary script>/ref/<ISA>/linux/
      The name of this directory should match the primary script (in tests/configs) that you want to execute.
  3. tests/ executes the python file tests/configs/<name of dir>.py
  4. After the file in tests/configs executes to completion, executes the secondary config file, or the file specific to this test
    The file is found in tests/<quick or long>/<se or fs>/<secondary script>/
    This file is usually used to specify the binary to simulate
  5. tests/ sets up some other parameters, like initializing CPUs.
  6. tests/ executes the function run_test(root)
    Note: At some point in the files that tests/ executes, you must specify a variable "root"
    You can overload run_test(root) by specifying it in one of the executed files. These files are executed in python as if their code were contained in
  7. Usually, in run_test(root), gem5 simulation is started.
  8. The output is written to build/<build to use>/tests/<binary name>/<quick or long>/<se or fs>/<secondary script>/<ISA>/linux/<primary script>
  9. The output is compared to the reference in tests/<quick or long>/<se or fs>/<secondary script>/ref/<ISA>/linux/<primary script>

Creating Your Own Regressions

Adding a regression test is done by adding a new directory to the 'm5/tests' directory and filling that directory up with the appropriate reference files. Every regression test needs these files in order to compare the current changes of M5 with the 'known working state:

  • simout - Standard Output Stream
  • simerr - Standard Error Stream
  • config.ini - M5 Configuration File
  • stats.txt - Statistics From M5 Simulation

One needs to run the M5 with the appropriate binary in order to get the aforementioned simulation files. For example, a command line to collect simulation data for a hello world regression test might be:

% build/ALPHA/ -re configs/example/ --cmd=tests/test-progs/hello/bin/alpha/hello

Creating the 'hello world' regression test directory and copying over the reference output might then follow this command line sequence:

% mkdir -p tests/quick/00.hello/ref/alpha/linux/simple-timing
% cp config.ini stats.txt simout simerr tests/quick/00.hello/ref/alpha/linux/simple-timing

You then need to create the test configuration file (e.g., in this case) in tests/configs, if it does not already exist. This file executes during tests/ In this file you must create a variable named "root", and you can optionally create function name run_test(root) which takes a single parameter (the root of the system). This function overloads a simple version in tests/

Next, you need to add your primary script name to the SConscript file in tests (tests/SConscript). In this file there is a variable named "configs". You need to add the name of you primary script to that list. Without this scons will not recognize your new test.

configs += ['simple-timing']

The last thing one needs to do is add a '' configuration file that specifies the workload for the regression test. For this 'hello world' example, the '' file would just contain:

root.system.cpu.workload = LiveProcess(cmd='hello', executable = binpath('hello'))

This file gets executed during tests/ after the primary script is executed.

Once the is copied to the 'hello world' regression test directory, the individual regression test can be run:

% cp tests/quick/00.hello
% scons build/ALPHA/tests/debug/quick/00.hello/alpha/linux/simple-timing

Or, you can execute all of the tests in 00.hello by running:

% scons build/ALPHA/tests/debug/quick/00.hello/

Updating Regression Tests

Once you've made and verified changes to the simulator, you can update any regression tests with the "update" option:

% scons --update-ref build/ALPHA/tests/debug/quick/00.hello