Re: [PATCH V2 06/13] selftests/resctrl: Remove "once" parameter required to be false

Ilpo Järvinen
2024-09-30T13:49:46Z

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On Thu, 12 Sep 2024, Reinette Chatre wrote:

> The CMT, MBM, and MBA tests rely on a benchmark that runs while
> the test makes changes to needed configuration (for example memory
> bandwidth allocation) and takes needed measurements. By default
> the "fill_buf" benchmark is used and by default (via its
> "once = false" setting) "fill_buf" is configured to run until
> terminated after the test completes.
>
> An unintended consequence of enabling the user to override the
> benchmark also enables the user to change parameters to the
> "fill_buf" benchmark. This enables the user to set "fill_buf" to
> only cycle through the buffer once (by setting "once = true")
> and thus breaking the CMT, MBA, and MBM tests that expect
> workload/interference to be reflected by their measurements.
>
> Prevent user space from changing the "once" parameter and ensure
> that it is always false for the CMT, MBA, and MBM tests.
>
> Suggested-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> Changes since V1:
> - New patch
> ---
> tools/testing/selftests/resctrl/fill_buf.c | 7 ++++---
> tools/testing/selftests/resctrl/resctrl.h | 2 +-
> tools/testing/selftests/resctrl/resctrl_tests.c | 8 +++++++-
> tools/testing/selftests/resctrl/resctrl_val.c | 11 +----------
> 4 files changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
> index 34e5df721430..854f0108d8e6 100644
> --- a/tools/testing/selftests/resctrl/fill_buf.c
> +++ b/tools/testing/selftests/resctrl/fill_buf.c
> @@ -151,7 +151,7 @@ unsigned char *alloc_buffer(size_t buf_size, int memflush)
> return buf;
> }
>
> -int run_fill_buf(size_t buf_size, int memflush, int op, bool once)
> +int run_fill_buf(size_t buf_size, int memflush, int op)
> {
> unsigned char *buf;
>
> @@ -160,9 +160,10 @@ int run_fill_buf(size_t buf_size, int memflush, int op, bool once)
> return -1;
>
> if (op == 0)
> - fill_cache_read(buf, buf_size, once);
> + fill_cache_read(buf, buf_size, false);
> else
> - fill_cache_write(buf, buf_size, once);
> + fill_cache_write(buf, buf_size, false);
> +
> free(buf);
>
> return 0;
> diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
> index 2dda56084588..51f5f4b25e06 100644
> --- a/tools/testing/selftests/resctrl/resctrl.h
> +++ b/tools/testing/selftests/resctrl/resctrl.h
> @@ -142,7 +142,7 @@ int perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu,
> unsigned char *alloc_buffer(size_t buf_size, int memflush);
> void mem_flush(unsigned char *buf, size_t buf_size);
> void fill_cache_read(unsigned char *buf, size_t buf_size, bool once);
> -int run_fill_buf(size_t buf_size, int memflush, int op, bool once);
> +int run_fill_buf(size_t buf_size, int memflush, int op);
> int initialize_mem_bw_imc(void);
> int measure_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 ecbb7605a981..bee4123a5a9b 100644
> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> @@ -266,7 +266,13 @@ int main(int argc, char **argv)
> uparams.benchmark_cmd[1] = span_str;
> uparams.benchmark_cmd[2] = "1";
> uparams.benchmark_cmd[3] = "0";
> - uparams.benchmark_cmd[4] = "false";
> + /*
> + * Fourth parameter was previously used to indicate
> + * how long "fill_buf" should run for, with "false"
> + * ("fill_buf" will keep running until terminated)
> + * the only option that works.
> + */
> + uparams.benchmark_cmd[4] = NULL;
> uparams.benchmark_cmd[5] = NULL;

Why is the [5] assignment kept around? Is something depending on this
double NULL termination? This patch removed the access to [4] so I
don't see anything beyong [3] accessed explicitly.

--
i.

> }
>
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index e88d5ca30517..5331354aaf64 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -625,7 +625,6 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
> int operation, ret, memflush;
> char **benchmark_cmd;
> size_t span;
> - bool once;
> FILE *fp;
>
> benchmark_cmd = info->si_ptr;
> @@ -645,16 +644,8 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
> span = strtoul(benchmark_cmd[1], NULL, 10);
> memflush = atoi(benchmark_cmd[2]);
> operation = atoi(benchmark_cmd[3]);
> - if (!strcmp(benchmark_cmd[4], "true")) {
> - once = true;
> - } else if (!strcmp(benchmark_cmd[4], "false")) {
> - once = false;
> - } else {
> - ksft_print_msg("Invalid once parameter\n");
> - parent_exit(ppid);
> - }
>
> - if (run_fill_buf(span, memflush, operation, once))
> + if (run_fill_buf(span, memflush, operation))
> fprintf(stderr, "Error in running fill buffer\n");
> } else {
> /* Execute specified benchmark */
>