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.cha...@intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvi...@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))) {
--
2.39.2
