| Message ID | ad51e32e5d4f8d99b691e7269e5179228e6a13a7.1726164080.git.reinette.chatre@intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | selftests/resctrl: Support diverse platforms with MBM and MBA tests | expand |
On Thu, 12 Sep 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> > --- > 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; > } > It has a bit of code duplication feel in it so I'd consider adding something like ssize_t get_default_span() (perhaps there exists a better name for it that is not "span" based). Also DEFAULT_SPAN is no longer truly the default span. But neither is the end of the world as is... Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Hi Ilpo, On 10/4/24 7:20 AM, Ilpo Järvinen wrote: > On Thu, 12 Sep 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> >> --- >> 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; >> } >> > > It has a bit of code duplication feel in it so I'd consider adding > something like ssize_t get_default_span() (perhaps there exists a better > name for it that is not "span" based). Also DEFAULT_SPAN is no longer > truly the default span. Good suggestion. How about get_fill_buf_size()? Regarding the "DEFAULT_SPAN" it seems to have some 'magic number smell' to it. When I tried to eliminate it and only rely on cache size the tests were failing on some earlier platforms with smaller L3. I then started treating it as a minimum in order to keep original behavior on these earlier systems. Perhaps renaming it to "MINIMUM_SPAN" would make this change clear? > > But neither is the end of the world as is... > > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> > > Thank you very much. Reinette
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; }
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(-)