Messages in this thread Patch in this message | | | Date | Tue, 22 Mar 2022 15:15:16 -0700 | Subject | [PATCH v7 12/13] perf tools: Improve error handling of AMD Branch Sampling | From | Stephane Eranian <> |
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Improve the error message printed by perf when perf_event_open() fails on AMD Zen3 when using the branch sampling feature. In the case of EINVAL, there are two main reasons: frequency mode or period is smaller than the depth of the branch sampling buffer (16). The patch checks the parameters of the call and tries to print a relevant message to explain the error:
$ perf record -b -e cpu/branch-brs/ -c 10 ls Error: AMD Branch Sampling does not support sampling period smaller than what is reported in /sys/devices/cpu/caps/branches.
$ perf record -b -e cpu/branch-brs/ ls Error: AMD Branch Sampling does not support frequency mode sampling, must pass a fixed sampling period via -c option or cpu/branch-brs,period=xxxx/.
Signed-off-by: Stephane Eranian <eranian@google.com> [Rebased on commit 9fe8895a27a84 ("perf env: Add perf_env__cpuid, perf_env__{nr_}pmu_mappings")] Signed-off-by: Kim Phillips <kim.phillips@amd.com> --- tools/perf/util/evsel.c | 43 ++++++++++++++++++++++++++++++----------- 1 file changed, 32 insertions(+), 11 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index e8ff7a4bd490..03f720a85764 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2858,6 +2858,16 @@ static bool is_amd_ibs(struct evsel *evsel) || (evsel->pmu_name && !strncmp(evsel->pmu_name, "ibs", 3)); } +static bool is_amd_brs_event(struct evsel *evsel) +{ + return (evsel->core.attr.config & 0xff) == 0xc4; +} + +static bool has_amd_brs(struct evsel *evsel) +{ + return (evsel->core.attr.sample_type & PERF_SAMPLE_BRANCH_STACK); +} + int evsel__open_strerror(struct evsel *evsel, struct target *target, int err, char *msg, size_t size) { @@ -2947,6 +2957,28 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target, "We found oprofile daemon running, please stop it and try again."); break; case EINVAL: + if (is_amd(arch, cpuid)) { + if (is_amd_ibs(evsel)) { + if (evsel->core.attr.exclude_kernel) + return scnprintf(msg, size, + "AMD IBS can't exclude kernel events. Try running at a higher privilege level."); + if (!evsel->core.system_wide) + return scnprintf(msg, size, + "AMD IBS may only be available in system-wide/per-cpu mode. Try using -a, or -C and workload affinity"); + } + if (has_amd_brs(evsel)) { + if (!is_amd_brs_event(evsel)) + return scnprintf(msg, size, + "AMD Branch Sampling can only be used with the cpu/branch-brs,period=xxxx/ event or equivalent encodings."); + if (evsel->core.attr.freq) + return scnprintf(msg, size, + "AMD Branch Sampling does not support frequency mode sampling, must pass a fixed sampling period via -c option or cpu/branch-brs,period=xxxx/."); + /* another reason is that the period is too small */ + return scnprintf(msg, size, + "AMD Branch Sampling does not support sampling period smaller than what is reported in /sys/devices/cpu/caps/branches."); + } + } + if (evsel->core.attr.sample_type & PERF_SAMPLE_CODE_PAGE_SIZE && perf_missing_features.code_page_size) return scnprintf(msg, size, "Asking for the code page size isn't supported by this kernel."); if (evsel->core.attr.sample_type & PERF_SAMPLE_DATA_PAGE_SIZE && perf_missing_features.data_page_size) @@ -2963,17 +2995,6 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target, return scnprintf(msg, size, "Invalid event (%s) in per-thread mode, enable system wide with '-a'.", evsel__name(evsel)); - if (is_amd(arch, cpuid)) { - if (is_amd_ibs(evsel)) { - if (evsel->core.attr.exclude_kernel) - return scnprintf(msg, size, - "AMD IBS can't exclude kernel events. Try running at a higher privilege level."); - if (!evsel->core.system_wide) - return scnprintf(msg, size, - "AMD IBS may only be available in system-wide/per-cpu mode. Try using -a, or -C and workload affinity"); - } - } - break; case ENODATA: return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. " -- 2.35.1.894.gb6a874cedc-goog
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