Re: [PATCH V2 09/13] selftests/resctrl: Make benchmark parameter passing robust

Ilpo Järvinen
2024-10-04T14:05:46Z

On Thu, 12 Sep 2024, Reinette Chatre wrote:

> The benchmark used during the CMT, MBM, and MBA tests can be provided by
> the user via (-b) parameter, if not provided the default "fill_buf"
> benchmark is used. The user is additionally able to override
> any of the "fill_buf" default parameters when running the tests with
> "-b fill_buf <fill_buf parameters>".
>
> The "fill_buf" parameters are managed as an array of strings. Using an
> array of strings is complex because it requires transformations to/from
> strings at every producer and consumer. This is made worse for the
> individual tests where the default benchmark parameters values may not
> be appropriate and additional data wrangling is required. For example,
> the CMT test duplicates the entire array of strings in order to replace
> one of the parameters.
>
> More issues appear when combining the usage of an array of strings with
> the use case of user overriding default parameters by specifying
> "-b fill_buf <parameters>". This use case is fragile with opportunities
> to trigger a SIGSEGV because of opportunities for NULL pointers to exist
> in the array of strings. For example, by running below (thus by specifying
> "fill_buf" should be used but all parameters are NULL):
> $ sudo resctrl_tests -t mbm -b fill_buf
>
> Replace the "array of strings" parameters used for "fill_buf" with
> new struct fill_buf_param that contains the "fill_buf" parameters that
> can be used directly without transformations to/from strings. Two
> instances of struct fill_buf_param may exist at any point in time:
> * If the user provides new parameters to "fill_buf", the
> user parameter structure (struct user_params) will point to a
> fully initialized and immutable struct fill_buf_param
> containing the user provided parameters.
> * If "fill_buf" is the benchmark that should be used by a test,
> then the test parameter structure (struct resctrl_val_param)
> will point to a fully initialized struct fill_buf_param. The
> latter may contain (a) the user provided parameters verbatim,
> (b) user provided parameters adjusted to be appropriate for
> the test, or (c) the default parameters for "fill_buf" that
> is appropriate for the test if the user did not provide
> "fill_buf" parameters nor an alternate benchmark.
>
> The existing behavior of CMT test is to use test defined value for the
> buffer size even if the user provides another value via command line.
> This behavior is maintained since the test requires that the buffer size
> matches the size of the cache allocated, and the amount of cache
> allocated can instead be changed by the user with the "-n" command line
> parameter.
>
> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
> ---
> Changes since V1:
> - Maintain original behavior where user can override "fill_buf"
> parameters via command line ... but only those that can actually
> be changed. (Ilpo)
> - Fix parsing issues associated with original behavior to ensure
> any parameter is valid before any attempt to use it.
> - Move patch earlier in series to highlight that this fixes existing
> issues.
> - Make struct fill_buf_param dynamic to support user provided
> parameters as well as test specific parameters.
> - Rewrite changelog.
> ---
> tools/testing/selftests/resctrl/cmt_test.c | 32 ++----
> tools/testing/selftests/resctrl/mba_test.c | 13 ++-
> tools/testing/selftests/resctrl/mbm_test.c | 22 ++--
> tools/testing/selftests/resctrl/resctrl.h | 54 ++++++---
> .../testing/selftests/resctrl/resctrl_tests.c | 104 +++++++++++++-----
> tools/testing/selftests/resctrl/resctrl_val.c | 43 ++++----
> 6 files changed, 176 insertions(+), 92 deletions(-)
>
> diff --git a/tools/testing/selftests/resctrl/cmt_test.c b/tools/testing/selftests/resctrl/cmt_test.c
> index 0c045080d808..a7effe76b419 100644
> --- a/tools/testing/selftests/resctrl/cmt_test.c
> +++ b/tools/testing/selftests/resctrl/cmt_test.c
> @@ -116,15 +116,13 @@ static void cmt_test_cleanup(void)
>
> static int cmt_run_test(const struct resctrl_test *test, const struct user_params *uparams)
> {
> - const char * const *cmd = uparams->benchmark_cmd;
> - const char *new_cmd[BENCHMARK_ARGS];
> + struct fill_buf_param fill_buf = {0};

Empty initializer is enough to have the fields initialized to zero.

> unsigned long cache_total_size = 0;
> int n = uparams->bits ? : 5;
> unsigned long long_mask;
> - char *span_str = NULL;
> int count_of_bits;
> size_t span;
> - int ret, i;
> + int ret;
>
> ret = get_full_cbm("L3", &long_mask);
> if (ret)
> @@ -155,32 +153,26 @@ static int cmt_run_test(const struct resctrl_test *test, const struct user_param
>
> span = cache_portion_size(cache_total_size, param.mask, long_mask);
>
> - if (strcmp(cmd[0], "fill_buf") == 0) {
> - /* Duplicate the command to be able to replace span in it */
> - for (i = 0; uparams->benchmark_cmd[i]; i++)
> - new_cmd[i] = uparams->benchmark_cmd[i];
> - new_cmd[i] = NULL;
> -
> - ret = asprintf(&span_str, "%zu", span);
> - if (ret < 0)
> - return -1;
> - new_cmd[1] = span_str;
> - cmd = new_cmd;
> + if (uparams->fill_buf) {
> + fill_buf.buf_size = span;
> + fill_buf.memflush = uparams->fill_buf->memflush;
> + param.fill_buf = &fill_buf;
> + } else if (!uparams->benchmark_cmd[0]) {
> + fill_buf.buf_size = span;
> + fill_buf.memflush = 1;
> + param.fill_buf = &fill_buf;
> }
>
> remove(RESULT_FILE_NAME);
>
> - ret = resctrl_val(test, uparams, cmd, &param);
> + ret = resctrl_val(test, uparams, &param);
> if (ret)
> - goto out;
> + return ret;
>
> ret = check_results(&param, span, n);
> if (ret && (get_vendor() == ARCH_INTEL))
> ksft_print_msg("Intel CMT may be inaccurate when Sub-NUMA Clustering is enabled. Check BIOS configuration.\n");
>
> -out:
> - free(span_str);
> -
> return ret;
> }
>
> diff --git a/tools/testing/selftests/resctrl/mba_test.c b/tools/testing/selftests/resctrl/mba_test.c
> index be0ead73e55d..7e43056c8737 100644
> --- a/tools/testing/selftests/resctrl/mba_test.c
> +++ b/tools/testing/selftests/resctrl/mba_test.c
> @@ -172,11 +172,22 @@ static int mba_run_test(const struct resctrl_test *test, const struct user_param
> .setup = mba_setup,
> .measure = mba_measure,
> };
> + struct fill_buf_param fill_buf = {0};

{}

> int ret;
>
> remove(RESULT_FILE_NAME);
>
> - ret = resctrl_val(test, uparams, uparams->benchmark_cmd, &param);
> + if (uparams->fill_buf) {
> + fill_buf.buf_size = uparams->fill_buf->buf_size;
> + fill_buf.memflush = uparams->fill_buf->memflush;
> + param.fill_buf = &fill_buf;
> + } else if (!uparams->benchmark_cmd[0]) {
> + fill_buf.buf_size = DEFAULT_SPAN;
> + fill_buf.memflush = 1;
> + param.fill_buf = &fill_buf;
> + }
> +
> + ret = resctrl_val(test, uparams, &param);
> if (ret)
> return ret;
>
> diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
> index 9744bf1ac16f..b1f03a73333f 100644
> --- a/tools/testing/selftests/resctrl/mbm_test.c
> +++ b/tools/testing/selftests/resctrl/mbm_test.c
> @@ -139,26 +139,26 @@ static int mbm_run_test(const struct resctrl_test *test, const struct user_param
> .setup = mbm_setup,
> .measure = mbm_measure,
> };
> - char *endptr = NULL;
> - size_t span = 0;
> + struct fill_buf_param fill_buf = {0};
> int ret;
>
> remove(RESULT_FILE_NAME);
>
> - if (uparams->benchmark_cmd[0] && strcmp(uparams->benchmark_cmd[0], "fill_buf") == 0) {
> - if (uparams->benchmark_cmd[1]) {
> - errno = 0;
> - span = strtoul(uparams->benchmark_cmd[1], &endptr, 10);
> - if (errno || uparams->benchmark_cmd[1] == endptr)
> - return -errno;
> - }
> + if (uparams->fill_buf) {
> + fill_buf.buf_size = uparams->fill_buf->buf_size;
> + fill_buf.memflush = uparams->fill_buf->memflush;
> + param.fill_buf = &fill_buf;
> + } else if (!uparams->benchmark_cmd[0]) {
> + fill_buf.buf_size = DEFAULT_SPAN;
> + fill_buf.memflush = 1;
> + param.fill_buf = &fill_buf;
> }
>
> - ret = resctrl_val(test, uparams, uparams->benchmark_cmd, &param);
> + ret = resctrl_val(test, uparams, &param);
> if (ret)
> return ret;
>
> - ret = check_results(span);
> + ret = check_results(param.fill_buf ? param.fill_buf->buf_size : 0);
> if (ret && (get_vendor() == ARCH_INTEL))
> ksft_print_msg("Intel MBM may be inaccurate when Sub-NUMA Clustering is enabled. Check BIOS configuration.\n");
>
> diff --git a/tools/testing/selftests/resctrl/resctrl.h b/tools/testing/selftests/resctrl/resctrl.h
> index 82801245e4c1..98462752cb46 100644
> --- a/tools/testing/selftests/resctrl/resctrl.h
> +++ b/tools/testing/selftests/resctrl/resctrl.h
> @@ -43,16 +43,35 @@
>
> #define DEFAULT_SPAN (250 * MB)
>
> +/*
> + * fill_buf_param: "fill_buf" benchmark parameters
> + * @buf_size: Size (in bytes) of buffer used in benchmark.
> + * "fill_buf" allocates and initializes buffer of
> + * @buf_size. User can change value via command line.
> + * @memflush: If 0 then the buffer will not be flushed after
> + * allocation and initialization, otherwise the
> + * buffer will be flushed. User can change value via
> + * command line.
> + */
> +struct fill_buf_param {
> + size_t buf_size;
> + int memflush;

bool?

Or is there a plan to use other values than 0 and 1?

> +};
> +
> /*
> * user_params: User supplied parameters
> * @cpu: CPU number to which the benchmark will be bound to
> * @bits: Number of bits used for cache allocation size
> * @benchmark_cmd: Benchmark command to run during (some of the) tests
> + * @fill_buf: Pointer to user provided parameters for "fill_buf",
> + * NULL if user did not provide parameters and test
> + * specific defaults should be used.
> */
> struct user_params {
> int cpu;
> int bits;
> const char *benchmark_cmd[BENCHMARK_ARGS];
> + const struct fill_buf_param *fill_buf;
> };
>
> /*
> @@ -87,21 +106,29 @@ struct resctrl_test {
> * @init: Callback function to initialize test environment
> * @setup: Callback function to setup per test run environment
> * @measure: Callback that performs the measurement (a single test)
> + * @fill_buf: Parameters for default "fill_buf" benchmark.
> + * Initialized with user provided parameters, possibly
> + * adapted to be relevant to the test. If user does
> + * not provide parameters for "fill_buf" nor a
> + * replacement benchmark then initialized with defaults
> + * appropriate for test. NULL if user provided
> + * benchmark.
> */
> struct resctrl_val_param {
> - const char *ctrlgrp;
> - const char *mongrp;
> - char filename[64];
> - unsigned long mask;
> - int num_of_runs;
> - int (*init)(const struct resctrl_val_param *param,
> - int domain_id);
> - int (*setup)(const struct resctrl_test *test,
> - const struct user_params *uparams,
> - struct resctrl_val_param *param);
> - int (*measure)(const struct user_params *uparams,
> - struct resctrl_val_param *param,
> - pid_t bm_pid);
> + const char *ctrlgrp;
> + const char *mongrp;
> + char filename[64];
> + unsigned long mask;
> + int num_of_runs;
> + int (*init)(const struct resctrl_val_param *param,
> + int domain_id);
> + int (*setup)(const struct resctrl_test *test,
> + const struct user_params *uparams,
> + struct resctrl_val_param *param);
> + int (*measure)(const struct user_params *uparams,
> + struct resctrl_val_param *param,
> + pid_t bm_pid);
> + struct fill_buf_param *fill_buf;
> };
>
> struct perf_event_read {
> @@ -149,7 +176,6 @@ void initialize_mem_bw_resctrl(const struct resctrl_val_param *param,
> int domain_id);
> int resctrl_val(const struct resctrl_test *test,
> const struct user_params *uparams,
> - const char * const *benchmark_cmd,
> struct resctrl_val_param *param);
> unsigned long create_bit_mask(unsigned int start, unsigned int len);
> unsigned int count_contiguous_bits(unsigned long val, unsigned int *start);
> diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
> index 60627dbae20a..121079363208 100644
> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> @@ -148,6 +148,78 @@ static void run_single_test(const struct resctrl_test *test, const struct user_p
> test_cleanup(test);
> }
>
> +/*
> + * Allocate and initialize a struct fill_buf_param with user provided
> + * (via "-b fill_buf <fill_buf parameters>") parameters.
> + *
> + * Use defaults (that may not be appropriate for all tests) for any
> + * fill_buf parameters omitted by the user.
> + *
> + * Historically it may have been possible for user space to provide
> + * additional parameters, "operation" ("read" vs "write") in
> + * benchmark_cmd[3] and "once" (run "once" or until terminated) in
> + * benchmark_cmd[4]. Changing these parameters have never been
> + * supported with the default of "read" operation and running until
> + * terminated built into the tests. Any unsupported values for
> + * (original) "fill_buf" parameters are treated as failure.
> + *
> + * Return: On failure, forcibly exits the test on any parsing failure,
> + * returns NULL if no parsing needed (user did not actually provide
> + * "-b fill_buf").
> + * On success, returns pointer to newly allocated and fully
> + * initialized struct fill_buf_param that caller must free.
> + */
> +static struct fill_buf_param *alloc_fill_buf_param(struct user_params *uparams)
> +{
> + struct fill_buf_param *fill_param = NULL;
> + char *endptr = NULL;
> +
> + if (!uparams->benchmark_cmd[0] || strcmp(uparams->benchmark_cmd[0], "fill_buf"))
> + return NULL;
> +
> + fill_param = malloc(sizeof(*fill_param));
> + if (!fill_param)
> + ksft_exit_skip("Unable to allocate memory for fill_buf parameters.\n");
> +
> + if (uparams->benchmark_cmd[1]) {
> + errno = 0;
> + fill_param->buf_size = strtoul(uparams->benchmark_cmd[1], &endptr, 10);
> + if (errno || uparams->benchmark_cmd[1] == endptr) {

Should this also check that there is no extra garbage?

> + free(fill_param);
> + ksft_exit_skip("Unable to parse benchmark buffer size.\n");
> + }
> + } else {
> + fill_param->buf_size = DEFAULT_SPAN;
> + }
> +
> + if (uparams->benchmark_cmd[2]) {
> + errno = 0;
> + fill_param->memflush = strtol(uparams->benchmark_cmd[2], &endptr, 10);
> + if (errno || uparams->benchmark_cmd[2] == endptr) {

Ditto ?

> + free(fill_param);
> + ksft_exit_skip("Unable to parse benchmark memflush parameter.\n");
> + }
> + } else {
> + fill_param->memflush = 1;

memflush could be bool ?

> + }
> +
> + if (uparams->benchmark_cmd[3]) {
> + if (strcmp(uparams->benchmark_cmd[3], "0")) {
> + free(fill_param);
> + ksft_exit_skip("Only read operations supported.\n");
> + }
> + }
> +
> + if (uparams->benchmark_cmd[4]) {
> + if (strcmp(uparams->benchmark_cmd[4], "false")) {
> + free(fill_param);
> + ksft_exit_skip("fill_buf is required to run until termination.\n");
> + }
> + }
> +
> + return fill_param;
> +}
> +
> static void init_user_params(struct user_params *uparams)
> {
> memset(uparams, 0, sizeof(*uparams));
> @@ -158,11 +230,11 @@ static void init_user_params(struct user_params *uparams)
>
> int main(int argc, char **argv)
> {
> + struct fill_buf_param *fill_param = NULL;
> int tests = ARRAY_SIZE(resctrl_tests);
> bool test_param_seen = false;
> struct user_params uparams;
> - char *span_str = NULL;
> - int ret, c, i;
> + int c, i;
>
> init_user_params(&uparams);
>
> @@ -239,6 +311,10 @@ int main(int argc, char **argv)
> }
> last_arg:
>
> + fill_param = alloc_fill_buf_param(&uparams);
> + if (fill_param)
> + uparams.fill_buf = fill_param;
> +
> ksft_print_header();
>
> /*
> @@ -257,33 +333,11 @@ int main(int argc, char **argv)
>
> filter_dmesg();
>
> - if (!uparams.benchmark_cmd[0]) {
> - /* If no benchmark is given by "-b" argument, use fill_buf. */
> - uparams.benchmark_cmd[0] = "fill_buf";
> - ret = asprintf(&span_str, "%u", DEFAULT_SPAN);
> - if (ret < 0)
> - ksft_exit_fail_msg("Out of memory!\n");
> - uparams.benchmark_cmd[1] = span_str;
> - uparams.benchmark_cmd[2] = "1";
> - /*
> - * Third parameter was previously used for "operation"
> - * (read/write) of which only (now default) "read"/"0"
> - * works.
> - * 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[3] = NULL;
> - uparams.benchmark_cmd[4] = NULL;
> - uparams.benchmark_cmd[5] = NULL;
> - }
> -
> ksft_set_plan(tests);
>
> for (i = 0; i < ARRAY_SIZE(resctrl_tests); i++)
> run_single_test(resctrl_tests[i], &uparams);
>
> - free(span_str);
> + free(fill_param);
> ksft_finished();
> }
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index a1e097dc8e05..380c3f218d01 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -535,6 +535,11 @@ int measure_read_mem_bw(const struct user_params *uparams,
> return ret;
> }
>
> +struct benchmark_info {
> + const struct user_params *uparams;
> + struct resctrl_val_param *param;
> +};
> +
> /*
> * run_benchmark - Run a specified benchmark or fill_buf (default benchmark)
> * in specified signal. Direct benchmark stdio to /dev/null.
> @@ -544,12 +549,15 @@ int measure_read_mem_bw(const struct user_params *uparams,
> */
> static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
> {
> - char **benchmark_cmd;
> - int ret, memflush;
> - size_t span;
> + struct benchmark_info *benchmark_info;
> + const struct user_params *uparams;
> + struct resctrl_val_param *param;
> FILE *fp;
> + int ret;
>
> - benchmark_cmd = info->si_ptr;
> + benchmark_info = info->si_ptr;

I'd just assign this directly while defining the local variable.

--
i.

> + uparams = benchmark_info->uparams;
> + param = benchmark_info->param;
>
> /*
> * Direct stdio of child to /dev/null, so that only parent writes to
> @@ -561,16 +569,13 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
> parent_exit(ppid);
> }
>
> - if (strcmp(benchmark_cmd[0], "fill_buf") == 0) {
> - /* Execute default fill_buf benchmark */
> - span = strtoul(benchmark_cmd[1], NULL, 10);
> - memflush = atoi(benchmark_cmd[2]);
> -
> - if (run_fill_buf(span, memflush))
> + if (param->fill_buf) {
> + if (run_fill_buf(param->fill_buf->buf_size,
> + param->fill_buf->memflush))
> fprintf(stderr, "Error in running fill buffer\n");
> - } else {
> + } else if (uparams->benchmark_cmd[0]) {
> /* Execute specified benchmark */
> - ret = execvp(benchmark_cmd[0], benchmark_cmd);
> + ret = execvp(uparams->benchmark_cmd[0], (char **)uparams->benchmark_cmd);
> if (ret)
> ksft_perror("execvp");
> }
> @@ -585,16 +590,15 @@ static void run_benchmark(int signum, siginfo_t *info, void *ucontext)
> * the benchmark
> * @test: test information structure
> * @uparams: user supplied parameters
> - * @benchmark_cmd: benchmark command and its arguments
> * @param: parameters passed to resctrl_val()
> *
> * Return: 0 when the test was run, < 0 on error.
> */
> int resctrl_val(const struct resctrl_test *test,
> const struct user_params *uparams,
> - const char * const *benchmark_cmd,
> struct resctrl_val_param *param)
> {
> + struct benchmark_info benchmark_info;
> struct sigaction sigact;
> int ret = 0, pipefd[2];
> char pipe_message = 0;
> @@ -610,6 +614,9 @@ int resctrl_val(const struct resctrl_test *test,
> return ret;
> }
>
> + benchmark_info.uparams = uparams;
> + benchmark_info.param = param;
> +
> /*
> * If benchmark wasn't successfully started by child, then child should
> * kill parent, so save parent's pid
> @@ -671,13 +678,7 @@ int resctrl_val(const struct resctrl_test *test,
>
> ksft_print_msg("Benchmark PID: %d\n", (int)bm_pid);
>
> - /*
> - * The cast removes constness but nothing mutates benchmark_cmd within
> - * the context of this process. At the receiving process, it becomes
> - * argv, which is mutable, on exec() but that's after fork() so it
> - * doesn't matter for the process running the tests.
> - */
> - value.sival_ptr = (void *)benchmark_cmd;
> + value.sival_ptr = (void *)&benchmark_info;
>
> /* Taskset benchmark to specified cpu */
> ret = taskset_benchmark(bm_pid, uparams->cpu, NULL);
>