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 that has been appropriate for testing so far.
Signed-off-by: Reinette Chatre reinette.chatre@intel.com --- Changes since V1: - Ensure buffer is at least double L3 cache size. (Ilpo) - Support user override of default buffer size. (Ilpo) --- tools/testing/selftests/resctrl/mba_test.c | 8 +++++++- tools/testing/selftests/resctrl/mbm_test.c | 8 +++++++- 2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c index 7e43056c8737..d8d9637c1951 100644 --- a/tools/testing/selftests/resctrl/mba_test.c +++ b/tools/testing/selftests/resctrl/mba_test.c @@ -182,7 +182,13 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param fill_buf.memflush = uparams->fill_buf->memflush; param.fill_buf = &fill_buf; } else if (!uparams->benchmark_cmd[0]) { - fill_buf.buf_size = DEFAULT_SPAN; + unsigned long cache_total_size = 0; + + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); + if (ret) + return ret; + fill_buf.buf_size = cache_total_size * 2 > DEFAULT_SPAN ? + cache_total_size * 2 : DEFAULT_SPAN; fill_buf.memflush = 1; param.fill_buf = &fill_buf; } diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c index b1f03a73333f..7635ee6b9339 100644 --- a/tools/testing/selftests/resctrl/mbm_test.c +++ b/tools/testing/selftests/resctrl/mbm_test.c @@ -149,7 +149,13 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param fill_buf.memflush = uparams->fill_buf->memflush; param.fill_buf = &fill_buf; } else if (!uparams->benchmark_cmd[0]) { - fill_buf.buf_size = DEFAULT_SPAN; + unsigned long cache_total_size = 0; + + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); + if (ret) + return ret; + fill_buf.buf_size = cache_total_size * 2 > DEFAULT_SPAN ? + cache_total_size * 2 : DEFAULT_SPAN; fill_buf.memflush = 1; param.fill_buf = &fill_buf; }