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

selftests/resctrl: Discover SNC kernel support and adjust messages

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

Resctrl selftest prints a message on test failure that Sub-Numa Clustering (SNC) could be enabled and points the user to check their BIOS settings. No actual check is performed before printing that message so it is not very accurate in pinpointing a problem. When there is SNC support for kernel's resctrl subsystem and SNC is enabled then sub node files are created for each node in the resctrlfs. The sub node files exist in each regular node's L3 monitoring directory. The reliable path to check for existence of sub node files is /sys/fs/resctrl/mon_data/mon_L3_00/mon_sub_L3_00. Add helper that checks for mon_sub_L3_00 existence. Correct old messages to account for kernel support of SNC in resctrl. Signed-off-by: Maciej Wieczor-Retman Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Keep results from first test run

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

The resctrl selftests drop the results from every first test run to avoid (per comment) "inaccurate due to monitoring setup transition phase" data. Previously inaccurate data resulted from workloads needing some time to "settle" and also the measurements themselves to account for earlier measurements to measure across needed timeframe. commit da50de0a92f3 ("selftests/resctrl: Calculate resctrl FS derived mem bw over sleep(1) only") ensured that measurements accurately measure just the time frame of interest. The default "fill_buf" benchmark since separated the buffer prepare phase from the benchmark run phase reducing the need for the tests themselves to accommodate the benchmark's "settle" time. With these enhancements there are no remaining portions needing to "settle" and the first test run can contribute to measurements. Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen 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: Remove unused measurement code

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

The MBM and MBA resctrl selftests run a benchmark during which it takes measurements of read memory bandwidth via perf. Code exists to support measurements of write memory bandwidth but there exists no path with which this code can execute. While code exists for write memory bandwidth measurement there has not yet been a use case for it. Remove this unused code. Rename relevant functions to include "read" so that it is clear that it relates only to memory bandwidth reads, while renaming the functions also add consistency by changing the "membw" instances to more prevalent "mem_bw". Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Print accurate buffer size as part of MBM results

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

By default the MBM test uses the "fill_buf" benchmark to keep reading from a buffer with size DEFAULT_SPAN while measuring memory bandwidth. User space can provide an alternate benchmark or amend the size of the buffer "fill_buf" should use. Analysis of the MBM measurements do not require that a buffer be used and thus do not require knowing the size of the buffer if it was used during testing. Even so, the buffer size is printed as informational as part of the MBM test results. What is printed as buffer size is hardcoded as DEFAULT_SPAN, even if the test relied on another benchmark (that may or may not use a buffer) or if user space amended the buffer size. Ensure that accurate buffer size is printed when using "fill_buf" benchmark and omit the buffer size information if another benchmark is used. Fixes: ecdbb911f22d ("selftests/resctrl: Add MBM test") Signed-off-by: Reinette Chatre Reviewed-by: Ilpo Järvinen Signed-off-by: Shuah Khan

selftests/resctrl: Remove test name comparing from write_bm_pid_to_resctrl()

2024-07-11T17:23:54+00:00

write_bm_pid_to_resctrl() uses resctrl_val to check test name which is not a good interface generic resctrl FS functions should provide. Tests define mongrp when needed. Remove the test name check in write_bm_pid_to_resctrl() to only rely on the mongrp parameter being non-NULL. Remove write_bm_pid_to_resctrl() resctrl_val parameter and resctrl_val member from the struct resctrl_val_param that are not used anymore. Similarly, remove the test name constants that are no longer used. Signed-off-by: Ilpo Järvinen Tested-by: Babu Moger Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Simplify bandwidth report type handling

2024-07-11T17:23:54+00:00

bw_report is only needed for selecting the correct value from the values IMC measured. It is a member in the resctrl_val_param struct and is always set to "reads". The value is then checked in resctrl_val() using validate_bw_report_request() that besides validating the input, assumes it can mutate the string which is questionable programming practice. Simplify handling bw_report: - Convert validate_bw_report_request() into get_bw_report_type() that inputs and returns const char *. Use NULL to indicate error. - Validate the report types inside measure_mem_bw(), not in resctrl_val(). - Pass bw_report to measure_mem_bw() from ->measure() hook because resctrl_val() no longer needs bw_report for anything. Signed-off-by: Ilpo Järvinen Tested-by: Babu Moger Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Add ->init() callback into resctrl_val_param

2024-07-11T17:23:54+00:00

The struct resctrl_val_param is there to customize behavior inside resctrl_val() which is currently not used to full extent and there are number of strcmp()s for test name in resctrl_val done by resctrl_val(). Create ->init() hook into the struct resctrl_val_param to cleanly do per test initialization. Remove also unused branches to setup paths and the related #defines for CMT test. While touching kerneldoc, make the adjacent line consistent with the newly added form (callback vs call back). Signed-off-by: Ilpo Järvinen Tested-by: Babu Moger Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan

selftests/resctrl: Add ->measure() callback to resctrl_val_param

2024-07-11T17:23:54+00:00

The measurement done in resctrl_val() varies depending on test type. The decision for how to measure is decided based on the string compare to test name which is quite inflexible. Add ->measure() callback into the struct resctrl_val_param to allow each test to provide necessary code as a function which simplifies what resctrl_val() has to do. Signed-off-by: Ilpo Järvinen Tested-by: Babu Moger Reviewed-by: Reinette Chatre Signed-off-by: Shuah Khan