On Thu, 17 Oct 2024, Reinette Chatre wrote:
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 reinette.chatre@intel.com
Look good, thanks.
Reviewed-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
-- i.
Changes since V2:
- Move duplicate code into helper. (Ilpo)
- Rename DEFAULT_SPAN to MINIMUM_SPAN to reflect its new purpose. (Ilpo)
- Do _not_ add Ilpo's Reviewed-by tag ... the patch changed too much.
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/fill_buf.c | 13 +++++++++++++ tools/testing/selftests/resctrl/mba_test.c | 7 ++++++- tools/testing/selftests/resctrl/mbm_test.c | 7 ++++++- tools/testing/selftests/resctrl/resctrl.h | 3 ++- tools/testing/selftests/resctrl/resctrl_tests.c | 2 +- 5 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c index 380cc35f10c6..19a01a52dc1a 100644 --- a/tools/testing/selftests/resctrl/fill_buf.c +++ b/tools/testing/selftests/resctrl/fill_buf.c @@ -129,3 +129,16 @@ unsigned char *alloc_buffer(size_t buf_size, bool memflush) return buf; }
+ssize_t get_fill_buf_size(int cpu_no, const char *cache_type) +{
- unsigned long cache_total_size = 0;
- int ret;
- ret = get_cache_size(cpu_no, cache_type, &cache_total_size);
- if (ret)
return ret;- return cache_total_size * 2 > MINIMUM_SPAN ?
cache_total_size * 2 : MINIMUM_SPAN;+} diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c index 74d95c460bd0..bf37f3555660 100644 --- a/tools/testing/selftests/resctrl/mba_test.c +++ b/tools/testing/selftests/resctrl/mba_test.c @@ -182,7 +182,12 @@ 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;
ssize_t buf_size;buf_size = get_fill_buf_size(uparams->cpu, "L3");if (buf_size < 0)return buf_size;fill_buf.buf_size = buf_size;diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c index 72261413c868..4224f8ce3538 100644 --- a/tools/testing/selftests/resctrl/mbm_test.c +++ b/tools/testing/selftests/resctrl/mbm_test.c @@ -149,7 +149,12 @@ 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;
ssize_t buf_size;buf_size = get_fill_buf_size(uparams->cpu, "L3");if (buf_size < 0)return buf_size;fill_buf.buf_size = buf_size;diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h index 032cd9ebd761..a553fe975938 100644 --- a/tools/testing/selftests/resctrl/resctrl.h +++ b/tools/testing/selftests/resctrl/resctrl.h @@ -41,7 +41,7 @@ #define BENCHMARK_ARGS 64 -#define DEFAULT_SPAN (250 * MB) +#define MINIMUM_SPAN (250 * MB) /*
- fill_buf_param: "fill_buf" benchmark parameters
@@ -169,6 +169,7 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu, unsigned char *alloc_buffer(size_t buf_size, bool memflush); void mem_flush(unsigned char *buf, size_t buf_size); void fill_cache_read(unsigned char *buf, size_t buf_size, bool once); +ssize_t get_fill_buf_size(int cpu_no, const char *cache_type); int initialize_read_mem_bw_imc(void); int measure_read_mem_bw(const struct user_params *uparams, struct resctrl_val_param *param, pid_t bm_pid); diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c index 88768f4d4961..790f4eb7871a 100644 --- a/tools/testing/selftests/resctrl/resctrl_tests.c +++ b/tools/testing/selftests/resctrl/resctrl_tests.c @@ -189,7 +189,7 @@ static struct fill_buf_param *alloc_fill_buf_param(struct user_params *uparams) ksft_exit_skip("Unable to parse benchmark buffer size.\n"); } } else {
fill_param->buf_size = DEFAULT_SPAN;
fill_param->buf_size = MINIMUM_SPAN;if (uparams->benchmark_cmd[2]) {