kernel/linux.git/tools/testing/selftests/resctrl/resctrl_tests.c, branch v6.19.11

selftests/resctrl: Adjust effective L3 cache size with SNC enabled

2025-01-15T00:06:32+00:00

Sub-NUMA Cluster divides CPUs sharing an L3 cache into separate NUMA nodes. Systems may support splitting into either two, three, four or six nodes. When SNC mode is enabled the effective amount of L3 cache available for allocation is divided by the number of nodes per L3. It's possible to detect which SNC mode is active by comparing the number of CPUs that share a cache with CPU0, with the number of CPUs on node0. Detect SNC mode once and let other tests inherit that information. Update CFLAGS after including lib.mk in the Makefile so that fallthrough macro can be used. To check if SNC detection is reliable one can check the /sys/devices/system/cpu/offline file. If it's empty, it means all cores are operational and the ratio should be calculated correctly. If it has any contents, it means the detected SNC mode can't be trusted and should be disabled. Check if detection was not reliable due to offline cpus. If it was skip running tests since the results couldn't be trusted. Co-developed-by: Tony Luck Signed-off-by: Tony Luck Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Use cache size to determine "fill_buf" buffer size

2024-11-05T00:02:03+00:00

By default the MBM and MBA tests use the "fill_buf" benchmark to read from a buffer with the goal to measure the memory bandwidth generated by this buffer access. Care should be taken when sizing the buffer used by the "fill_buf" benchmark. If the buffer is small enough to fit in the cache then it cannot be expected that the benchmark will generate much memory bandwidth. For example, on a system with 320MB L3 cache the existing hardcoded default of 250MB is insufficient. Use the measured cache size to determine a buffer size that can be expected to trigger memory access while keeping the existing default as minimum, now renamed to MINIMUM_SPAN, that has been appropriate for testing so far. Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Make benchmark parameter passing robust

2024-11-05T00:02:03+00:00

The benchmark used during the CMT, MBM, and MBA tests can be provided by the user via (-b) parameter, if not provided the default "fill_buf" benchmark is used. The user is additionally able to override any of the "fill_buf" default parameters when running the tests with "-b fill_buf ". The "fill_buf" parameters are managed as an array of strings. Using an array of strings is complex because it requires transformations to/from strings at every producer and consumer. This is made worse for the individual tests where the default benchmark parameters values may not be appropriate and additional data wrangling is required. For example, the CMT test duplicates the entire array of strings in order to replace one of the parameters. More issues appear when combining the usage of an array of strings with the use case of user overriding default parameters by specifying "-b fill_buf ". This use case is fragile with opportunities to trigger a SIGSEGV because of opportunities for NULL pointers to exist in the array of strings. For example, by running below (thus by specifying "fill_buf" should be used but all parameters are NULL): $ sudo resctrl_tests -t mbm -b fill_buf Replace the "array of strings" parameters used for "fill_buf" with new struct fill_buf_param that contains the "fill_buf" parameters that can be used directly without transformations to/from strings. Two instances of struct fill_buf_param may exist at any point in time: * If the user provides new parameters to "fill_buf", the user parameter structure (struct user_params) will point to a fully initialized and immutable struct fill_buf_param containing the user provided parameters. * If "fill_buf" is the benchmark that should be used by a test, then the test parameter structure (struct resctrl_val_param) will point to a fully initialized struct fill_buf_param. The latter may contain (a) the user provided parameters verbatim, (b) user provided parameters adjusted to be appropriate for the test, or (c) the default parameters for "fill_buf" that is appropriate for the test if the user did not provide "fill_buf" parameters nor an alternate benchmark. The existing behavior of CMT test is to use test defined value for the buffer size even if the user provides another value via command line. This behavior is maintained since the test requires that the buffer size matches the size of the cache allocated, and the amount of cache allocated can instead be changed by the user with the "-n" command line parameter. Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Only support measured read operation

2024-11-05T00:02:03+00:00

The CMT, MBM, and MBA tests rely on a benchmark to generate memory traffic. By default this is the "fill_buf" benchmark that can be replaced via the "-b" command line argument. The original intent of the "-b" command line parameter was to replace the default "fill_buf" benchmark, but the implementation also exposes an alternative use case where the "fill_buf" parameters itself can be modified. One of the parameters to "fill_buf" is the "operation" that can be either "read" or "write" and indicates whether the "fill_buf" should use "read" or "write" operations on the allocated buffer. While replacing "fill_buf" default parameters is technically possible, replacing the default "read" parameter with "write" is not supported because the MBA and MBM tests only measure "read" operations. The "read" operation is also most appropriate for the CMT test that aims to use the benchmark to allocate into the cache. Avoid any potential inconsistencies between test and measurement by removing code for unsupported "write" operations to the buffer. Ignore any attempt from user space to enable this unsupported test configuration, instead always use read operations. Keep the initialization of the, now unused, "fill_buf" parameters to reserve these parameter positions since it has been exposed as an API. Future parameter additions cannot use these parameter positions. Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Remove "once" parameter required to be false

2024-11-05T00:02:03+00:00

The CMT, MBM, and MBA tests rely on a benchmark that runs while the test makes changes to needed configuration (for example memory bandwidth allocation) and takes needed measurements. By default the "fill_buf" benchmark is used and by default (via its "once = false" setting) "fill_buf" is configured to run until terminated after the test completes. An unintended consequence of enabling the user to override the benchmark also enables the user to change parameters to the "fill_buf" benchmark. This enables the user to set "fill_buf" to only cycle through the buffer once (by setting "once = true") and thus breaking the CMT, MBA, and MBM tests that expect workload/interference to be reflected by their measurements. Prevent user space from changing the "once" parameter and ensure that it is always false for the CMT, MBA, and MBM tests. Suggested-by: Ilpo Järvinen Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: ksft_exit_skip() does not return

2024-05-06T19:57:20+00:00

After commit f7d5bcd35d42 ("selftests: kselftest: Mark functions that unconditionally call exit() as __noreturn"), ksft_exit_...() functions are marked as __noreturn, which means the return type should not be 'int' but 'void' because they are not returning anything (and never were since exit() has always been called). To facilitate updating the return type of these functions, remove 'return' before the calls to ksft_exit_skip(), as __noreturn prevents the compiler from warning that a caller of ksft_exit_skip() does not return a value because the program will terminate upon calling these functions. Reviewed-by: Muhammad Usama Anjum Reviewed-by: Thomas Gleixner Signed-off-by: Nathan Chancellor Signed-off-by: Shuah Khan

selftests/resctrl: Move cleanups out of individual tests

2024-05-06T19:57:19+00:00

Every test calls its cleanup function at the end of it's test function. After the cleanup function pointer is added to the test framework this can be simplified to executing the callback function at the end of the generic test running function. Make test cleanup functions static and call them from the end of run_single_test() from the resctrl_test's cleanup function pointer. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Simplify cleanup in ctrl-c handler

2024-05-06T19:57:19+00:00

Ctrl-c handler isn't aware of what test is currently running. Because of that it executes all cleanups even if they aren't necessary. Since the ctrl-c handler uses the sa_sigaction system no parameters can be passed to it as function arguments. Add a global variable to make ctrl-c handler aware of the currently run test and only execute the correct cleanup callback. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Add non-contiguous CBMs CAT test

2024-02-23T22:19:25+00:00

Add tests for both L2 and L3 CAT to verify the return values generated by writing non-contiguous CBMs don't contradict the reported non-contiguous support information. Use a logical XOR to confirm return value of write_schemata() and non-contiguous CBMs support information match. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Add test groups and name L3 CAT test L3_CAT

2024-02-23T22:19:03+00:00

To select test to run -t parameter can be used. However, -t cat currently maps to L3 CAT test which will be confusing after more CAT related tests will be added. Allow selecting tests as groups and call L3 CAT test "L3_CAT", "CAT" group will enable all CAT related tests. Signed-off-by: Ilpo Järvinen Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan