Messages in this thread | | | Date | Thu, 9 Nov 2023 16:56:15 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 2/2] perf header: Additional note on AMD IBS for max_precise pmu cap |
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Em Tue, Nov 07, 2023 at 02:03:31PM +0530, Ravi Bangoria escreveu: > From: Arnaldo Carvalho de Melo <acme@kernel.org>
Applied this one, waiting for some more time to address Ian comments,
- Arnaldo
> x86 core pmu exposes supported maximum precision level via max_precise > pmu capability. Although, AMD core pmu does not support precise mode, > certain core pmu events with precise_ip > 0 are allowed and forwarded > to IBS OP pmu. Display a note about this in perf report header and > document the details in the perf-list man page. > > Signed-off-by: Arnaldo Carvalho de Melo <acme@kernel.org> > Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com> > --- > tools/perf/Documentation/perf-list.txt | 12 +++++++----- > tools/perf/util/env.c | 18 ++++++++++++++++++ > tools/perf/util/env.h | 2 ++ > tools/perf/util/header.c | 8 ++++++++ > 4 files changed, 35 insertions(+), 5 deletions(-) > > diff --git a/tools/perf/Documentation/perf-list.txt b/tools/perf/Documentation/perf-list.txt > index d5f78e125efe..1b90575ee3c8 100644 > --- a/tools/perf/Documentation/perf-list.txt > +++ b/tools/perf/Documentation/perf-list.txt > @@ -81,11 +81,13 @@ For Intel systems precise event sampling is implemented with PEBS > which supports up to precise-level 2, and precise level 3 for > some special cases > > -On AMD systems it is implemented using IBS (up to precise-level 2). > -The precise modifier works with event types 0x76 (cpu-cycles, CPU > -clocks not halted) and 0xC1 (micro-ops retired). Both events map to > -IBS execution sampling (IBS op) with the IBS Op Counter Control bit > -(IbsOpCntCtl) set respectively (see the > +On AMD systems it is implemented using IBS OP (up to precise-level 2). > +Unlike Intel PEBS which provides levels of precision, AMD core pmu is > +inherently non-precise and IBS is inherently precise. (i.e. ibs_op//, > +ibs_op//p, ibs_op//pp and ibs_op//ppp are all same). The precise modifier > +works with event types 0x76 (cpu-cycles, CPU clocks not halted) and 0xC1 > +(micro-ops retired). Both events map to IBS execution sampling (IBS op) > +with the IBS Op Counter Control bit (IbsOpCntCtl) set respectively (see the > Core Complex (CCX) -> Processor x86 Core -> Instruction Based Sampling (IBS) > section of the [AMD Processor Programming Reference (PPR)] relevant to the > family, model and stepping of the processor being used). > diff --git a/tools/perf/util/env.c b/tools/perf/util/env.c > index 44140b7f596a..cbc18b22ace5 100644 > --- a/tools/perf/util/env.c > +++ b/tools/perf/util/env.c > @@ -531,6 +531,24 @@ int perf_env__numa_node(struct perf_env *env, struct perf_cpu cpu) > return cpu.cpu >= 0 && cpu.cpu < env->nr_numa_map ? env->numa_map[cpu.cpu] : -1; > } > > +bool perf_env__has_pmu_mapping(struct perf_env *env, const char *pmu_name) > +{ > + char *pmu_mapping = env->pmu_mappings, *colon; > + > + for (int i = 0; i < env->nr_pmu_mappings; ++i) { > + if (strtoul(pmu_mapping, &colon, 0) == ULONG_MAX || *colon != ':') > + goto out_error; > + > + pmu_mapping = colon + 1; > + if (strcmp(pmu_mapping, pmu_name) == 0) > + return true; > + > + pmu_mapping += strlen(pmu_mapping) + 1; > + } > +out_error: > + return false; > +} > + > char *perf_env__find_pmu_cap(struct perf_env *env, const char *pmu_name, > const char *cap) > { > diff --git a/tools/perf/util/env.h b/tools/perf/util/env.h > index 4566c51f2fd9..56aea562c61b 100644 > --- a/tools/perf/util/env.h > +++ b/tools/perf/util/env.h > @@ -174,4 +174,6 @@ struct btf_node *perf_env__find_btf(struct perf_env *env, __u32 btf_id); > int perf_env__numa_node(struct perf_env *env, struct perf_cpu cpu); > char *perf_env__find_pmu_cap(struct perf_env *env, const char *pmu_name, > const char *cap); > + > +bool perf_env__has_pmu_mapping(struct perf_env *env, const char *pmu_name); > #endif /* __PERF_ENV_H */ > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index e86b9439ffee..3cc288d14002 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -2145,6 +2145,14 @@ static void print_pmu_caps(struct feat_fd *ff, FILE *fp) > __print_pmu_caps(fp, pmu_caps->nr_caps, pmu_caps->caps, > pmu_caps->pmu_name); > } > + > + if (strcmp(perf_env__arch(&ff->ph->env), "x86") == 0 && > + perf_env__has_pmu_mapping(&ff->ph->env, "ibs_op")) { > + char *max_precise = perf_env__find_pmu_cap(&ff->ph->env, "cpu", "max_precise"); > + > + if (max_precise != NULL && atoi(max_precise) == 0) > + fprintf(fp, "# AMD systems uses ibs_op// PMU for some precise events, e.g.: cycles:p, see the 'perf list' man page for further details.\n"); > + } > } > > static void print_pmu_mappings(struct feat_fd *ff, FILE *fp) > -- > 2.41.0 >
--
- Arnaldo
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