Messages in this thread | | | Date | Mon, 17 Apr 2023 09:58:35 -0400 | Subject | Re: [PATCH v2] perf stat: Introduce skippable evsels | From | "Liang, Kan" <> |
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On 2023-04-14 7:03 p.m., Ian Rogers wrote: > 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:
The above multiplexing should be on a Skylake (since there is no topdownL1 printed), but the test which you repeat seems on a Tigerlake (has topdownL1). Could you please double check on a Skylake?
Thanks, Kan > > ``` > $ 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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