Messages in this thread Patch in this message | | | Date | Wed, 16 Feb 2022 11:17:53 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v6 11/12] perf tools: Improve error handling of AMD Branch Sampling |
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Em Tue, Feb 08, 2022 at 01:16:36PM -0800, Stephane Eranian escreveu: > 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 | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index d42f63a484df..7311e7b4d34d 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -2857,6 +2857,12 @@ static bool is_amd_ibs(struct evsel *evsel) > return evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3); > } > > +static bool is_amd_brs(struct evsel *evsel) > +{ > + return ((evsel->core.attr.config & 0xff) == 0xc4) && > + (evsel->core.attr.sample_type & PERF_SAMPLE_BRANCH_STACK); > +} > +
Well, this assumes we're on x86_64, right? Shouldn't we have some extra condition using perf_env routines to check we're on x86_64.
Did a quick check and powerpc also supports PERF_SAMPLE_BRANCH_STACK
⬢[acme@toolbox perf]$ find arch/ -name "*.c" | xargs grep PERF_SAMPLE_BRANCH_STACK arch/powerpc/perf/core-book3s.c: if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) { arch/x86/events/intel/ds.c: if (sample_type & PERF_SAMPLE_BRANCH_STACK) { arch/x86/events/intel/ds.c: PERF_SAMPLE_BRANCH_STACK | arch/x86/events/intel/lbr.c: * in PERF_SAMPLE_BRANCH_STACK sample may vary. arch/x86/kvm/vmx/pmu_intel.c: * - set 'sample_type = PERF_SAMPLE_BRANCH_STACK' and arch/x86/kvm/vmx/pmu_intel.c: .sample_type = PERF_SAMPLE_BRANCH_STACK, ⬢[acme@toolbox perf]$
arch/powerpc/perf/core-book3s.c:
if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) { struct cpu_hw_events *cpuhw; cpuhw = this_cpu_ptr(&cpu_hw_events); power_pmu_bhrb_read(event, cpuhw); data.br_stack = &cpuhw->bhrb_stack; }
> int evsel__open_strerror(struct evsel *evsel, struct target *target, > int err, char *msg, size_t size) > { > @@ -2971,6 +2977,14 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target, > 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 (is_amd_brs(evsel)) { > + 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."); > + } > } > > break; > -- > 2.35.0.263.gb82422642f-goog
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- Arnaldo
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