For MBM/MBA tests, measure_vals() calls get_mem_bw_imc() that performs the measurement over a duration of sleep(1) call. The memory bandwidth numbers from IMC are derived over this duration. The resctrl FS derived memory bandwidth, however, is calculated inside measure_vals() and only takes delta between the previous value and the current one which besides the actual test, also samples inter-test noise.
Rework the logic in measure_vals() and get_mem_bw_imc() such that the resctrl FS memory bandwidth section covers much shorter duration closely matching that of the IMC perf counters to improve measurement accuracy.
Suggested-by: Reinette Chatre reinette.chatre@intel.com Signed-off-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com --- tools/testing/selftests/resctrl/resctrl_val.c | 72 +++++++++++++------ 1 file changed, 50 insertions(+), 22 deletions(-)
diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c index 36139cba7be8..4df2cd738f88 100644 --- a/tools/testing/selftests/resctrl/resctrl_val.c +++ b/tools/testing/selftests/resctrl/resctrl_val.c @@ -293,28 +293,35 @@ static int initialize_mem_bw_imc(void) }
/* - * get_mem_bw_imc: Memory band width as reported by iMC counters + * perf_open_imc_mem_bw - Open perf fds for IMCs * @cpu_no: CPU number that the benchmark PID is binded to - * @bw_report: Bandwidth report type (reads, writes) - * - * Memory B/W utilized by a process on a socket can be calculated using - * iMC counters. Perf events are used to read these counters. - * - * Return: = 0 on success. < 0 on failure. */ -static int get_mem_bw_imc(int cpu_no, char *bw_report, float *bw_imc) +static int perf_open_imc_mem_bw(int cpu_no) { - float reads, writes, of_mul_read, of_mul_write; int imc, j, ret;
- /* Start all iMC counters to log values (both read and write) */ - reads = 0, writes = 0, of_mul_read = 1, of_mul_write = 1; for (imc = 0; imc < imcs; imc++) { for (j = 0; j < 2; j++) { ret = open_perf_event(imc, cpu_no, j); if (ret) return -1; } + } + + return 0; +} + +/* + * do_mem_bw_test - Perform memory bandwidth test + * + * Runs memory bandwidth test over one second period. Also, handles starting + * and stopping of the IMC perf counters around the test. + */ +static void do_imc_mem_bw_test(void) +{ + int imc, j; + + for (imc = 0; imc < imcs; imc++) { for (j = 0; j < 2; j++) membw_ioctl_perf_event_ioc_reset_enable(imc, j); } @@ -326,6 +333,24 @@ static int get_mem_bw_imc(int cpu_no, char *bw_report, float *bw_imc) for (j = 0; j < 2; j++) membw_ioctl_perf_event_ioc_disable(imc, j); } +} + +/* + * get_mem_bw_imc - Memory band width as reported by iMC counters + * @bw_report: Bandwidth report type (reads, writes) + * + * Memory B/W utilized by a process on a socket can be calculated using + * iMC counters. Perf events are used to read these counters. + * + * Return: = 0 on success. < 0 on failure. + */ +static int get_mem_bw_imc(char *bw_report, float *bw_imc) +{ + float reads, writes, of_mul_read, of_mul_write; + int imc, j; + + /* Start all iMC counters to log values (both read and write) */ + reads = 0, writes = 0, of_mul_read = 1, of_mul_write = 1;
/* * Get results which are stored in struct type imc_counter_config @@ -593,10 +618,9 @@ static void initialize_llc_occu_resctrl(const char *ctrlgrp, const char *mongrp, }
static int measure_vals(const struct user_params *uparams, - struct resctrl_val_param *param, - unsigned long *bw_resc_start) + struct resctrl_val_param *param) { - unsigned long bw_resc, bw_resc_end; + unsigned long bw_resc, bw_resc_start, bw_resc_end; float bw_imc; int ret;
@@ -607,22 +631,27 @@ static int measure_vals(const struct user_params *uparams, * Compare the two values to validate resctrl value. * It takes 1sec to measure the data. */ - ret = get_mem_bw_imc(uparams->cpu, param->bw_report, &bw_imc); + ret = perf_open_imc_mem_bw(uparams->cpu); if (ret < 0) return ret;
+ ret = get_mem_bw_resctrl(&bw_resc_start); + if (ret < 0) + return ret; + + do_imc_mem_bw_test(); + ret = get_mem_bw_resctrl(&bw_resc_end); if (ret < 0) return ret;
- bw_resc = (bw_resc_end - *bw_resc_start) / MB; - ret = print_results_bw(param->filename, bm_pid, bw_imc, bw_resc); - if (ret) + ret = get_mem_bw_imc(param->bw_report, &bw_imc); + if (ret < 0) return ret;
- *bw_resc_start = bw_resc_end; + bw_resc = (bw_resc_end - bw_resc_start) / MB;
- return 0; + return print_results_bw(param->filename, bm_pid, bw_imc, bw_resc); }
/* @@ -696,7 +725,6 @@ int resctrl_val(const struct resctrl_test *test, struct resctrl_val_param *param) { char *resctrl_val = param->resctrl_val; - unsigned long bw_resc_start = 0; struct sigaction sigact; int ret = 0, pipefd[2]; char pipe_message = 0; @@ -838,7 +866,7 @@ int resctrl_val(const struct resctrl_test *test,
if (!strncmp(resctrl_val, MBM_STR, sizeof(MBM_STR)) || !strncmp(resctrl_val, MBA_STR, sizeof(MBA_STR))) { - ret = measure_vals(uparams, param, &bw_resc_start); + ret = measure_vals(uparams, param); if (ret) break; } else if (!strncmp(resctrl_val, CMT_STR, sizeof(CMT_STR))) {