| Message ID | d357189fe0695b2140fc03efde75edc6fa0c88c6.1724970211.git.reinette.chatre@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | selftests/resctrl: Support diverse platforms with MBM and MBA tests | expand |
On Thu, 29 Aug 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 that has been appropriate for testing so far. > > Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> > --- > 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 8ad433495f61..cad473b81a64 100644 > --- a/tools/testing/selftests/resctrl/mba_test.c > +++ b/tools/testing/selftests/resctrl/mba_test.c > @@ -170,11 +170,17 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param > .setup = mba_setup, > .measure = mba_measure, > }; > + unsigned long cache_total_size = 0; > int ret; > > remove(RESULT_FILE_NAME); > > - param.fill_buf.buf_size = DEFAULT_SPAN; > + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); > + if (ret) > + return ret; > + > + param.fill_buf.buf_size = cache_total_size > DEFAULT_SPAN ? > + cache_total_size * 2 : DEFAULT_SPAN; Should the check leave a bit of safeguard so that the buf_size is at least 2x (or x1.25 or some other factor)? In here buf_size immediate jumps from 1x -> 2x when cache_total_size goes from DEFAULT_SPAN to DEFAULT_SPAN+1 (obviously L3 size won't be odd like that but I think you get my point). Also, user might want to override this as mentioned in my reply to the previous patch.
Hi Ilpo, On 8/30/24 4:25 AM, Ilpo Järvinen wrote: > On Thu, 29 Aug 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 that has been appropriate for testing so far. >> >> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> >> --- >> 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 8ad433495f61..cad473b81a64 100644 >> --- a/tools/testing/selftests/resctrl/mba_test.c >> +++ b/tools/testing/selftests/resctrl/mba_test.c >> @@ -170,11 +170,17 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param >> .setup = mba_setup, >> .measure = mba_measure, >> }; >> + unsigned long cache_total_size = 0; >> int ret; >> >> remove(RESULT_FILE_NAME); >> >> - param.fill_buf.buf_size = DEFAULT_SPAN; >> + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); >> + if (ret) >> + return ret; >> + >> + param.fill_buf.buf_size = cache_total_size > DEFAULT_SPAN ? >> + cache_total_size * 2 : DEFAULT_SPAN; > > Should the check leave a bit of safeguard so that the buf_size is at > least 2x (or x1.25 or some other factor)? > > In here buf_size immediate jumps from 1x -> 2x when cache_total_size goes > from DEFAULT_SPAN to DEFAULT_SPAN+1 (obviously L3 size won't be odd like > that but I think you get my point). Good catch. Will fix. > > Also, user might want to override this as mentioned in my reply to the > previous patch. > ack. Reinette
diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c index 8ad433495f61..cad473b81a64 100644 --- a/tools/testing/selftests/resctrl/mba_test.c +++ b/tools/testing/selftests/resctrl/mba_test.c @@ -170,11 +170,17 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param .setup = mba_setup, .measure = mba_measure, }; + unsigned long cache_total_size = 0; int ret; remove(RESULT_FILE_NAME); - param.fill_buf.buf_size = DEFAULT_SPAN; + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); + if (ret) + return ret; + + param.fill_buf.buf_size = cache_total_size > DEFAULT_SPAN ? + cache_total_size * 2 : DEFAULT_SPAN; param.fill_buf.memflush = 1; param.fill_buf.operation = 0; param.fill_buf.once = false; diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c index b6883f274c74..734bfa4f42b3 100644 --- a/tools/testing/selftests/resctrl/mbm_test.c +++ b/tools/testing/selftests/resctrl/mbm_test.c @@ -138,11 +138,17 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param .setup = mbm_setup, .measure = mbm_measure, }; + unsigned long cache_total_size = 0; int ret; remove(RESULT_FILE_NAME); - param.fill_buf.buf_size = DEFAULT_SPAN; + ret = get_cache_size(uparams->cpu, "L3", &cache_total_size); + if (ret) + return ret; + + param.fill_buf.buf_size = cache_total_size > DEFAULT_SPAN ? + cache_total_size * 2 : DEFAULT_SPAN; param.fill_buf.memflush = 1; param.fill_buf.operation = 0; param.fill_buf.once = false;
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> --- tools/testing/selftests/resctrl/mba_test.c | 8 +++++++- tools/testing/selftests/resctrl/mbm_test.c | 8 +++++++- 2 files changed, 14 insertions(+), 2 deletions(-)