Messages in this thread Patch in this message | | | From | Ian Rogers <> | Date | Fri, 14 Apr 2023 16:03:56 -0700 | Subject | Re: [PATCH v2] perf stat: Introduce skippable evsels |
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On Fri, Apr 14, 2023 at 11:07 AM Liang, Kan <kan.liang@linux.intel.com> wrote: > > > > On 2023-04-14 1:19 a.m., Ian Rogers wrote: > > Perf stat with no arguments will use default events and metrics. These > > events may fail to open even with kernel and hypervisor disabled. When > > these fail then the permissions error appears even though they were > > implicitly selected. This is particularly a problem with the automatic > > selection of the TopdownL1 metric group on certain architectures like > > Skylake: > > > > ``` > > $ perf stat true > > Error: > > Access to performance monitoring and observability operations is limited. > > Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open > > access to performance monitoring and observability operations for processes > > without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability. > > More information can be found at 'Perf events and tool security' document: > > https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html > > perf_event_paranoid setting is 2: > > -1: Allow use of (almost) all events by all users > > Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK > >> = 0: Disallow raw and ftrace function tracepoint access > >> = 1: Disallow CPU event access > >> = 2: Disallow kernel profiling > > To make the adjusted perf_event_paranoid setting permanent preserve it > > in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>) > > ``` > > > > This patch adds skippable evsels that when they fail to open won't > > fail and won't appear in output. The TopdownL1 events, from the metric > > group, are marked as skippable. This turns the failure above to: > > > > ``` > > $ perf stat true > > > > Performance counter stats for 'true': > > > > 1.26 msec task-clock:u # 0.328 CPUs utilized > > 0 context-switches:u # 0.000 /sec > > 0 cpu-migrations:u # 0.000 /sec > > 49 page-faults:u # 38.930 K/sec > > 176,449 cycles:u # 0.140 GHz (48.99%) > > Multiplexing? > > Thanks, > Kan
I may have been running a test in the background otherwise I can't explain it. Repeating the test yields no multiplexing:
``` $ perf stat true
Performance counter stats for 'true':
0.78 msec task-clock:u # 0.383 CPUs utilized 0 context-switches:u # 0.000 /sec 0 cpu-migrations:u # 0.000 /sec 47 page-faults:u # 60.174 K/sec 233,420 cycles:u # 0.299 GHz 133,318 instructions:u # 0.57 insn per cycle 31,396 branches:u # 40.196 M/sec 2,334 branch-misses:u # 7.43% of all branches 1,167,100 TOPDOWN.SLOTS:u # 12.2 % tma_retiring # 28.9 % tma_backend_bound # 41.0 % tma_frontend_bound # 18.0 % tma_bad_speculation 141,882 topdown-retiring:u 480,570 topdown-fe-bound:u 320,380 topdown-be-bound:u 224,266 topdown-bad-spec:u 2,173 INT_MISC.UOP_DROPPING:u # 2.782 M/sec 3,323 cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/u # 4.254 M/sec
0.002036744 seconds time elapsed
0.002252000 seconds user 0.000000000 seconds sys ```
Thanks, Ian
> > 122,905 instructions:u # 0.70 insn per cycle > > 28,264 branches:u # 22.456 M/sec > > 2,405 branch-misses:u # 8.51% of all branches > > > > 0.003834565 seconds time elapsed > > > > 0.000000000 seconds user > > 0.004130000 seconds sys > > ``` > > > > When the events can have kernel/hypervisor disabled, like on > > Tigerlake, then it continues to succeed as: > > > > ``` > > $ perf stat true > > > > Performance counter stats for 'true': > > > > 0.57 msec task-clock:u # 0.385 CPUs utilized > > 0 context-switches:u # 0.000 /sec > > 0 cpu-migrations:u # 0.000 /sec > > 47 page-faults:u # 82.329 K/sec > > 287,017 cycles:u # 0.503 GHz > > 133,318 instructions:u # 0.46 insn per cycle > > 31,396 branches:u # 54.996 M/sec > > 2,442 branch-misses:u # 7.78% of all branches > > 998,790 TOPDOWN.SLOTS:u # 14.5 % tma_retiring > > # 27.6 % tma_backend_bound > > # 40.9 % tma_frontend_bound > > # 17.0 % tma_bad_speculation > > 144,922 topdown-retiring:u > > 411,266 topdown-fe-bound:u > > 258,510 topdown-be-bound:u > > 184,090 topdown-bad-spec:u > > 2,585 INT_MISC.UOP_DROPPING:u # 4.528 M/sec > > 3,434 cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/u # 6.015 M/sec > > > > 0.001480954 seconds time elapsed > > > > 0.000000000 seconds user > > 0.001686000 seconds sys > > ``` > > > > And this likewise works if paranoia allows or running as root. > > > > v2. Don't display the skipped events as <not counted> or <not supported>. > > > > Signed-off-by: Ian Rogers <irogers@google.com> > > --- > > tools/perf/builtin-stat.c | 39 ++++++++++++++++++++++++++-------- > > tools/perf/util/evsel.c | 15 +++++++++++-- > > tools/perf/util/evsel.h | 1 + > > tools/perf/util/stat-display.c | 4 ++++ > > 4 files changed, 48 insertions(+), 11 deletions(-) > > > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > > index d3cbee7460fc..7a641a67486d 100644 > > --- a/tools/perf/builtin-stat.c > > +++ b/tools/perf/builtin-stat.c > > @@ -667,6 +667,13 @@ static enum counter_recovery stat_handle_error(struct evsel *counter) > > evsel_list->core.threads->err_thread = -1; > > return COUNTER_RETRY; > > } > > + } else if (counter->skippable) { > > + if (verbose > 0) > > + ui__warning("skipping event %s that kernel failed to open .\n", > > + evsel__name(counter)); > > + counter->supported = false; > > + counter->errored = true; > > + return COUNTER_SKIP; > > } > > > > evsel__open_strerror(counter, &target, errno, msg, sizeof(msg)); > > @@ -1885,15 +1892,29 @@ static int add_default_attributes(void) > > * Add TopdownL1 metrics if they exist. To minimize > > * multiplexing, don't request threshold computation. > > */ > > - if (metricgroup__has_metric("TopdownL1") && > > - metricgroup__parse_groups(evsel_list, "TopdownL1", > > - /*metric_no_group=*/false, > > - /*metric_no_merge=*/false, > > - /*metric_no_threshold=*/true, > > - stat_config.user_requested_cpu_list, > > - stat_config.system_wide, > > - &stat_config.metric_events) < 0) > > - return -1; > > + if (metricgroup__has_metric("TopdownL1")) { > > + struct evlist *metric_evlist = evlist__new(); > > + struct evsel *metric_evsel; > > + > > + if (!metric_evlist) > > + return -1; > > + > > + if (metricgroup__parse_groups(metric_evlist, "TopdownL1", > > + /*metric_no_group=*/false, > > + /*metric_no_merge=*/false, > > + /*metric_no_threshold=*/true, > > + stat_config.user_requested_cpu_list, > > + stat_config.system_wide, > > + &stat_config.metric_events) < 0) > > + return -1; > > + > > + evlist__for_each_entry(metric_evlist, metric_evsel) { > > + metric_evsel->skippable = true; > > + } > > + evlist__splice_list_tail(evsel_list, &metric_evlist->core.entries); > > + evlist__delete(metric_evlist); > > + } > > + > > /* Platform specific attrs */ > > if (evlist__add_default_attrs(evsel_list, default_null_attrs) < 0) > > return -1; > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > > index a85a987128aa..83a65f771666 100644 > > --- a/tools/perf/util/evsel.c > > +++ b/tools/perf/util/evsel.c > > @@ -290,6 +290,7 @@ void evsel__init(struct evsel *evsel, > > evsel->per_pkg_mask = NULL; > > evsel->collect_stat = false; > > evsel->pmu_name = NULL; > > + evsel->skippable = false; > > } > > > > struct evsel *evsel__new_idx(struct perf_event_attr *attr, int idx) > > @@ -1720,9 +1721,13 @@ static int get_group_fd(struct evsel *evsel, int cpu_map_idx, int thread) > > return -1; > > > > fd = FD(leader, cpu_map_idx, thread); > > - BUG_ON(fd == -1); > > + BUG_ON(fd == -1 && !leader->skippable); > > > > - return fd; > > + /* > > + * When the leader has been skipped, return -2 to distinguish from no > > + * group leader case. > > + */ > > + return fd == -1 ? -2 : fd; > > } > > > > static void evsel__remove_fd(struct evsel *pos, int nr_cpus, int nr_threads, int thread_idx) > > @@ -2104,6 +2109,12 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, > > > > group_fd = get_group_fd(evsel, idx, thread); > > > > + if (group_fd == -2) { > > + pr_debug("broken group leader for %s\n", evsel->name); > > + err = -EINVAL; > > + goto out_close; > > + } > > + > > test_attr__ready(); > > > > /* Debug message used by test scripts */ > > diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h > > index 68072ec655ce..98afe3351176 100644 > > --- a/tools/perf/util/evsel.h > > +++ b/tools/perf/util/evsel.h > > @@ -95,6 +95,7 @@ struct evsel { > > bool weak_group; > > bool bpf_counter; > > bool use_config_name; > > + bool skippable; > > int bpf_fd; > > struct bpf_object *bpf_obj; > > struct list_head config_terms; > > diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c > > index e6035ecbeee8..6b46bbb3d322 100644 > > --- a/tools/perf/util/stat-display.c > > +++ b/tools/perf/util/stat-display.c > > @@ -810,6 +810,10 @@ static bool should_skip_zero_counter(struct perf_stat_config *config, > > struct perf_cpu cpu; > > int idx; > > > > + /* Skip counters that were speculatively/default enabled rather than requested. */ > > + if (counter->skippable) > > + return true; > > + > > /* > > * Skip value 0 when enabling --per-thread globally, > > * otherwise it will have too many 0 output.
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