Tests for SCHED_DEADLINE

This is a minimal set of unit tests for the SCHED_DEADLINE Linux scheduler, especially for the GRUB algorithm introduced with release 4.13.

The scripts allow to test and visualize on kernelshark the behavior of the scheduler under several circumstances (e.g., task migration, switch to CFS, parameters change, etc.).

The work has been done in the context of the HERCULES European project and has been used to validate the implementation of the GRUB algorithm.

Target requirements

• A Linux kernel 3.14+ compiled with the following symbols:
  • CONFIG_FTRACE
  • CONFIG_FTRACE_SYSCALLS
  • CONFIG_CPUSETS=y
  • CONFIG_CGROUPS=y
  • CONFIG_CGROUP_SCHED=y
  • CONFIG_FAIR_GROUP_SCHED=y
  • CONFIG_PROC_PID_CPUSET=y
  • CONFIG_CGROUP_PIDS=y
• A Linux distribution with the following packages installed:
  • make
  • gcc
  • xinit
  • trace-cmd
  • kernelshark
  • psmisc
  • xterm

Note: besides visualizing the kernelshark trace, you may want to instrument the code in deadline.c with trace_printk() instructions to check the behavior of specific portions of code. In particular, the directory kernel-patches contains an example of patch to trace the runqueues' bandwidths of GRUB.

Usage

• Clean old results:

         make clean
  

• Build:

         make
  

• Run

         sudo ./run.sh [test]
  

  Note: for testing the reclaiming feature of GRUB, uncomment TESTDL_SCHED_FLAG=2 inside run.sh.

• Then, check the results with

         ./check.sh [test]
  

• Alternatively, the tests can be also run and checked using ARM's LISA framework. The directory lisa contains an example of notebook for running the test suite from LISA.

trace-cmd installation

The trace-cmd and kernelshark tools are available by default in the repositories of most Linux distributions. If you rather prefer to download and build these tools from sources:

• Install the needed build packages:

        sudo apt-get install build-essential gnome-devel
  

• Get the source code of trace-cmd:

        git clone git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git
  
        git checkout trace-cmd-v2.6
  

• Build the tools:

        cd test-dl
  
        make
  
        make gui
  

• Change inside run.sh and in check.sh the variables TRACECMD and KERNELSHARK, respectively.

Code coverage

• Build the kernel with the following additional symbols:

  • CONFIG_DEBUG_FS
  • CONFIG_GCOV_KERNEL
  • CONFIG_GCOV_FORMAT_AUTODETECT

• Add

         GCOV_PROFILE_deadline.o := y
  

  to kernel/sched/Makefile

• On the target, mount debugfs if it is not yet mounted:

         mount -t debugfs none /sys/kernel/debug
  

• Run the tests

• Copy *.gcda and *.gcno files from /sys/kernel/debug/gcov/ to your build machine e.g. in directory /tmp/gcov

• For gcov, enter the directory of the built kernel and type

         (your_toolchain)-gcov -o /tmp/gcov deadline.c
  

  Then, read the produced .gcov file

• Alternatively, for lcov (frontend to gcov), enter the directory of the built kernel and type

         lcov -c --base-directory . -d /tmp/gcov/ --output-file coverage.info
  
         genhtml -o /tmp/coverage/ coverage.info
  

  Then, enter directory /tmp/coverage and open index.html.

• Note: currently, the tests cover 84% of the deadline.c file (including the code executed at boot time by Linux).