Re: [PATCH v1 11/13] perf tools: improve IBS error handling

From: Arnaldo Carvalho de Melo
Date: Mon Sep 13 2021 - 15:34:32 EST


Em Thu, Sep 09, 2021 at 12:56:58AM -0700, Stephane Eranian escreveu:
> From: Kim Phillips <kim.phillips@xxxxxxx>
>
> This patch improves the error message returned on failed perf_event_open() on
> AMD when using IBS.
>
> Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
> ---
> tools/perf/util/evsel.c | 42 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index f61e5dd53f5d..f203f178fdb9 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2684,12 +2684,52 @@ static bool find_process(const char *name)
> return ret ? false : true;
> }
>
> +static bool is_amd;
> +
> +static char *fgrep(FILE *inf, const char *str)
> +{
> + char line[256];
> + int slen = strlen(str);
> +
> + while (!feof(inf)) {
> + if (!fgets(line, 256, inf))
> + break;
> + if (strncmp(line, str, slen))
> + continue;
> +
> + return strdup(line);
> + }
> +
> + return NULL;
> +}
> +
> +static void detect_amd(void)
> +{
> + FILE *inf = fopen("/proc/cpuinfo", "r");
> + char *res;
> +
> + if (!inf)
> + return;
> +
> + res = fgrep(inf, "vendor_id");
> +
> + if (res) {
> + char *s = strchr(res, ':');
> +
> + is_amd = s && !strcmp(s, ": AuthenticAMD\n");
> + free(res);
> + }
> + fclose(inf);
> +}
> +

We have perf_env for such details, for instance in
tools/perf/util/sample-raw.c we have:o

const char *arch_pf = perf_env__arch(evlist->env);
const char *cpuid = perf_env__cpuid(evlist->env);

else if (arch_pf && !strcmp("x86", arch_pf) &&
cpuid && strstarts(cpuid, "AuthenticAMD") &&
evlist__has_amd_ibs(evlist)) {



> int evsel__open_strerror(struct evsel *evsel, struct target *target,
> int err, char *msg, size_t size)
> {
> char sbuf[STRERR_BUFSIZE];
> int printed = 0, enforced = 0;
>
> + detect_amd();
> +
> switch (err) {
> case EPERM:
> case EACCES:
> @@ -2782,6 +2822,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
> return scnprintf(msg, size, "wrong clockid (%d).", clockid);
> if (perf_missing_features.aux_output)
> return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
> + if (is_amd && (evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3)) && (evsel->core.attr.exclude_kernel))
> + return scnprintf(msg, size, "AMD IBS can't exclude kernel events. Try running at a higher privilege level.");
> break;
> case ENODATA:
> return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
> --
> 2.33.0.153.gba50c8fa24-goog

--

- Arnaldo