Strategy and Workflow
Due to the amount of data that LKFT produces, test results need to be clear and actionable. This means there is a very low tolerance for any tests which sometimes pass and sometimes fail. Further, any test that is expected to fail is marked as a known issue in qa-reports so that results are always in a ‘all green’ state. This makes triaging new regressions straightforward.
Whenever a test becomes a known issue, a bug is opened in bugzilla. All bugzilla bugs are regularly reviewed, investigated, and reported internally or upstream.
All regressions are triaged and reported internally and/or upstream. Typically the test will also be added as a known issue until it is fixed.
Running Test Suites
Linux Test Project (LTP)
The following test sets are run in LTP:
The version of LTP used is the most recent release, plus backports that fix regressions, if any.
LTP issues are tracked in several places.
Bugs are tracked in bugzilla and can be seen at bugs.linaro.org (query for product ‘Kernel Functional Testing’ and component ‘Linux Test Project (LTP)’).
A skipfile is maintained which contains a list of tests that are not suitable to run for a variety of reasons. LKFT’s LTP skipfile can be found in test-definitions repository.
Finally, known issues are used to annotate failures in qa-reports, so that known failures show up as ‘xfail’ (expected fail), instead of a failure. The known issues that LKFT uses in LTP can be found at qa-reports-known-issues.
Linux Kernel Selftests
Linux Kernel Selftests, or kselftests, are tests that are included in the linux kernel tree under tools/testing/selftests/.
The version used depends on the kernel version under test:
- linux-next uses selftest included in linux-next
- mainline uses selftest included in mainline
- Latest stable uses selftest included in latest stable
- All other LTS branches also use the version from latest stable
Running a mismatched kselftest version does create false positives from time to time, but it is the best balance between a supported and up to date set of tests and an older kernel.
Kselftest issues are tracked in several places.
Bugs are tracked in bugzilla and can be seen at bugs.linaro.org (query for product ‘Kernel Functional Testing’ and component ‘kselftest’).
A skipfile is maintained which contains a list of tests that are not suitable to run for a variety of reasons. LKFT’s Kselftest skipfile can be found in test-definitions repository.
Finally, known issues are used to annotate failures in qa-reports, so that known failures show up as ‘xfail’ (expected fail), instead of a failure. The known issues that LKFT uses in kselftest can be found at qa-reports-known-issues.
libhugetlbfs is run using the latest released version.
LKFT Integration with Perf testing on Arm64
Build Kernel with extra debug configurations
Except the default config, we need to enable extra Linux kernel configurations for building kernel image. Below is some missed configurations that we can enable with the commands:
export ARCH=arm64 export CROSS_COMPILE=aarch64-linux-gnu- cd $LINUX_SRC make defconfig ./scripts/config -e CONFIG_BPF_SYSCALL ./scripts/config -e CONFIG_BPF_JIT_ALWAYS_ON ./scripts/config -e CONFIG_TRACEPOINTS ./scripts/config -e CONFIG_KPROBES ./scripts/config -e CONFIG_UPROBES ./scripts/config -e CONFIG_KRETPROBES ./scripts/config -e CONFIG_PROC_KCORE ./scripts/config -e CONFIG_NOP_TRACER ./scripts/config -e CONFIG_TRACER_MAX_TRACE ./scripts/config -e CONFIG_RING_BUFFER ./scripts/config -e CONFIG_EVENT_TRACING ./scripts/config -e CONFIG_CONTEXT_SWITCH_TRACER ./scripts/config -e CONFIG_TRACING ./scripts/config -e CONFIG_GENERIC_TRACER ./scripts/config -e CONFIG_FTRACE ./scripts/config -e CONFIG_FUNCTION_TRACER ./scripts/config -e CONFIG_FUNCTION_GRAPH_TRACER ./scripts/config -e CONFIG_SCHED_TRACER ./scripts/config -e CONFIG_FTRACE_SYSCALLS ./scripts/config -e CONFIG_TRACER_SNAPSHOT ./scripts/config -e CONFIG_KPROBE_EVENTS ./scripts/config -e CONFIG_UPROBE_EVENTS ./scripts/config -e CONFIG_BPF_EVENTS ./scripts/config -e CONFIG_DYNAMIC_EVENTS ./scripts/config -e CONFIG_PROBE_EVENTS ./scripts/config -e CONFIG_DYNAMIC_FTRACE yes "" | make oldconfig
Installation dependency libs on target board
# apt-get install flex bison libelf-dev libaudit-dev libdw-dev libunwind* python-dev binutils-dev \ libnuma-dev libbfd-dev libelf1 libperl-dev libslang2 libslang2-dev libunwind8 libunwind8-dev \ binutils-multiarch-dev elfutils libiberty-dev libncurses5-dev # apt-get install clang-7 llvm-7
The kernel source code path
The kernel source code is fatal for ‘perf probe’ related testings; usually, on Arm platform the perf probe related testings fail due to perf tool cannot find the kernel source code path.
On x86 platform, it’s quite common to use the same PC to build kernel and perf tool, and then can directly run the perf test on it. Thus it’s smooth for x86 to allow debugging tools to find the source code path based on vmlinux’s dwarf info.
On the other hand, Arm platforms, usually, we cross compile kernel image on our PC or laptop and then run the testing on Arm boards. So the issue is perf tool uses the vmlinux’s dwarf info to find the source code path but the path is PC’s path but not the kernel source code path on the target board.
To fix this issue, the simple method is to create the same path on Arm platforms with the PC; for example, on the PC side, build the kernel in the folder “/home/leoy/Work/opensource/linux-cs-dev”; then on Arm board, should create the path “/home/leoy/Work/opensource/linux-cs-dev” and mount NFS on this folder. Thus the Arm board can use the same code base and this allows perf tool to easily to find kernel source code.
Exporting perf python lib
Perf provides python’s .so, which needs to tell python the right path to export ‘perf’ class. This can be finished with below command:
Perf config file
We need to configure clang related options thus allows perf tool to have knowledge for clang and llvm:
# cd $LINUX_SRC # ./tools/perf/perf config llvm.clang-path=clang-7 # ./tools/perf/perf config llvm.kbuild-dir=/home/leoy/Work/opensource/linux-cs-dev/ # ./tools/perf/perf config llvm.clang-opt="-g"
# cd $LINUX_SRC # ./tools/perf/perf test
|Test ID||Test Case||DB410c||Juno||Comment|
|1||vmlinux symtab matches kallsyms||Ok||Ok||vmlinux must be placed in the current folder.|
|2||Detect openat syscall event||Ok||Ok|
|3||Detect openat syscall event on all cpus||Ok||Ok|
|4||Read samples using the mmap interface||Ok||Ok|
|5||Test data source output||Ok||Ok|
|6||Parse event definition strings||Ok||Ok|
|7||Simple expression parser||Ok||Ok|
|8||PERF_RECORD_* events & perf_sample fields||Ok||Ok|
|9||Parse perf pmu format||Ok||Ok|
|10||DSO data read||Ok||Ok|
|11||DSO data cache||Ok||Ok|
|12||DSO data reopen||Ok||Ok|
|14||Parse sched tracepoints fields||Ok||Ok|
|15||syscalls:sys_enter_openat event fields||Ok||Ok|
|16||Setup struct perf_event_attr||Ok||Ok|
|17||Match and link multiple hists||Ok||Ok|
|18||‘import perf’ in python||Ok||Ok|
|19||Breakpoint overflow signal handler||Disabled||Disabled||The signal handler doesn’t work well with breakpoint on Arm/Arm64.|
|20||Breakpoint overflow sampling||Disabled||Disabled||The signal handler doesn’t work well with breakpoint on Arm/Arm64.|
|22.1||Read Only Watchpoint||Ok||Ok|
|22.2||Write Only Watchpoint||Ok||Ok|
|22.3||Read / Write Watchpoint||Ok||Ok|
|23||Number of exit events of a simple workload||Ok||FAILED||Any big.LITTLE system cannot migrate events between different CPU variants, thus this case will fail on big.LITTLE system. This case can pass on SMP platform (e.g. DB410c).|
|24||Software clock events period values||Ok||Ok|
|25||Object code reading||Ok||Ok|
|27||Use a dummy software event to keep tracking||Ok||Ok|
|28||Parse with no sample_id_all bit set||Ok||Ok|
|29||Filter hist entries||Ok||Ok|
|30||Lookup mmap thread||Ok||Ok|
|31||Share thread mg||Ok||Ok|
|32||Sort output of hist entries||Ok||Ok|
|33||Cumulate child hist entries||Ok||Ok|
|34||Track with sched_switch||Ok||Ok|
|35||Filter fds with revents mask in a fdarray||Ok||Ok|
|36||Add fd to a fdarray, making it autogrow||Ok||Ok|
|39.1||Basic BPF llvm compile||Ok||Ok|
|39.3||Compile source for BPF prologue generation||Ok||Ok|
|39.4||Compile source for BPF relocation||Ok||Ok|
|41.1||Basic BPF filtering||Ok||Ok|
|41.3||BPF prologue generation||Ok||Ok|
|41.4||BPF relocation checker||Ok||Ok|
|42||Synthesize thread map||Ok||Ok|
|43||Remove thread map||Ok||Ok|
|44||Synthesize cpu map||Ok||Ok|
|45||Synthesize stat config||Ok||Ok|
|47||Synthesize stat round||Ok||Ok|
|48||Synthesize attr update||Ok||Ok|
|50||Read backward ring buffer||Ok||Ok|
|51||Print cpu map||Ok||Ok|
|52||Probe SDT events||Ok||Ok|
|56||builtin clang support||Skip||Skip|
|62||probe libc’s inet_pton & backtrace it with ping||Skip||Skip|
|63||Check open filename arg using perf trace + vfs_getname||Ok||Ok||If fail, the failure is caused by cannot find kernel source code.|
|64||Zstd perf.data compression/decompression||Skip||Skip|
|65||Add vfs_getname probe to get syscall args filenames||Ok||Ok||If fail, the failure is caused by cannot find kernel source code.|
|66||Use vfs_getname probe to get syscall args filenames||Ok||Ok||If fail, the failure is caused by cannot find kernel source code.|
The v4l2-compliance tests are run using a virtual driver (VIVI)
KVM Unit Tests
KVM-unit-tests are run to verify basic functionality of KVM.
S I/O Benchmark Suite are enabled for a subset of systems to verify I/O performance.
For the moment, this test makes it possible to execute the following two benchmarks with the suite:
- responsiveness, by measuring start-up times of real applications under real background workloads;
- throughput with processes doing filesystem or raw I/O in parallel (figure of merit measured by many other suites too).
Separate test runs of KUnit are enabled for Qemu on x86 (64/32 bits) and arm (64/32 bits).
Future Test Suites
We are continuously evaluating test suites for use in LKFT. We are guided by feedback from kernel engineers and the community at large. If you would like to see a particular test or test suite added to LKFT, please contact us.