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Date: Fri, 10 May 2024 17:50:29 -0700
From: Ian Rogers <irogers@...gle.com>
To: Justin He <Justin.He@....com>, John Garry <john.g.garry@...cle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Mark Rutland <Mark.Rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>,
James Clark <James.Clark@....com>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, nd <nd@....com>
Subject: Re: [PATCH 2/2] perf pmu: Fix num_events calculation
On Fri, May 10, 2024 at 1:41 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Thu, May 9, 2024 at 11:52 PM Justin He <Justin.He@....com> wrote:
> >
> > Hi, Ian
> >
> > > -----Original Message-----
> > > From: Ian Rogers <irogers@...gle.com>
> > > Sent: Friday, May 10, 2024 2:17 PM
> > > To: Justin He <Justin.He@....com>
> > > Cc: Peter Zijlstra <peterz@...radead.org>; Ingo Molnar <mingo@...hat.com>;
> > > Arnaldo Carvalho de Melo <acme@...nel.org>; Namhyung Kim
> > > <namhyung@...nel.org>; Mark Rutland <Mark.Rutland@....com>; Alexander
> > > Shishkin <alexander.shishkin@...ux.intel.com>; Jiri Olsa <jolsa@...nel.org>;
> > > Adrian Hunter <adrian.hunter@...el.com>; Kan Liang
> > > <kan.liang@...ux.intel.com>; James Clark <James.Clark@....com>;
> > > linux-perf-users@...r.kernel.org; linux-kernel@...r.kernel.org
> > > Subject: Re: [PATCH 2/2] perf pmu: Fix num_events calculation
> > >
> > > On Thu, May 9, 2024 at 7:47 PM Jia He <justin.he@....com> wrote:
> > > >
> > > > When pe is NULL in the function perf_pmu__new_alias(), the total
> > > > number of events is added to loaded_json_aliases. However, if
> > > > pmu->events_table is NULL and cpu_aliases_added is false, the
> > > > calculation for the events number in perf_pmu__num_events() is incorrect.
> > > >
> > > > Then cause the error report after "perf list":
> > > > Unexpected event
> > > smmuv3_pmcg_3f062/smmuv3_pmcg_3f062/transaction//
> > > >
> > > > Fix it by adding loaded_json_aliases in the calculation under the
> > > > mentioned conditions.
> > > >
> > > > Test it also with "perf bench internals pmu-scan" and there is no
> > > > regression.
> > > >
> > > > Fixes: e6ff1eed3584 ("perf pmu: Lazily add JSON events")
> > > > Signed-off-by: Jia He <justin.he@....com>
> > > > ---
> > > > tools/perf/util/pmu.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c index
> > > > a1eef7b2e389..a53224e2ce7e 100644
> > > > --- a/tools/perf/util/pmu.c
> > > > +++ b/tools/perf/util/pmu.c
> > > > @@ -1639,6 +1639,8 @@ size_t perf_pmu__num_events(struct perf_pmu
> > > *pmu)
> > > > nr += pmu->loaded_json_aliases;
> > > > else if (pmu->events_table)
> > > > nr +=
> > > pmu_events_table__num_events(pmu->events_table,
> > > > pmu) - pmu->loaded_json_aliases;
> > > > + else
> > > > + nr += pmu->loaded_json_aliases;
> > >
> > > Thanks for working on this! The "struct pmu_event *pe" in new_alias is an entry
> > > from the json data, and "pmu->events_table" should NULL if there is no json
> > > data. I believe the code is assuming that these lines aren't necessary as it
> > > shouldn't be possible to load json data if the json events table doesn't exist for
> > > the PMU - if there is no json data then loaded_json_aliases should be 0 and no
> > > addition is necessary. I'm wondering why this case isn't true for you.
> > On my Armv8a N2 server, "pmu->events_table" is NULL because perf_pmu__find_events_table()
> > return NULL.
> >
> > I also noticed that pmu->loaded_json_aliases is *not* 0. The missing adding calculation will cause
> > perf_pmu__num_events() less than normal case and will trigger latter check failure in
> > perf_pmus__print_pmu_events__callback().
> > At last, perf list will report many lines similar as:
> > Unexpected event smmuv3_pmcg_3f062/smmuv3_pmcg_3f062/transaction//
>
> The issue is the sys events which currently are ARM only. Here is an
> lldb stack trace:
> ```
> frame #6: 0x0000aaaaabc9b49c
> perf`__assert_fail(assertion="pmu->events_table",
> file="tools/perf/util/pmu.c", line=522, function="int
> perf_pmu__new_alias(struct perf_pmu *, const char *, const char *,
> const char *, FILE *, const struct pmu_event *)")
> frame #7: 0x0000aaaaab41e018
> perf`perf_pmu__new_alias(pmu=0x00007377e7e09b40,
> name="hnf_brd_snoops_sent", desc="Counts number of multicast snoops
> sent (not including SF back invalidation)", val="eventid=9,type=5",
> val_fd=0x0000000000000000, pe=0x0000ffffffffde88) at pmu.c:522:3
> frame #8: 0x0000aaaaab4175cc
> perf`pmu_add_sys_aliases_iter_fn(pe=0x0000ffffffffde88,
> table=0x0000aaaaac299bb0, vdata=0x00007377e7e09b40) at pmu.c:939:3
> frame #9: 0x0000aaaaaaf6d000
> perf`pmu_events_table__for_each_event_pmu(table=0x0000aaaaac299bb0,
> pmu=0x0000aaaaac299238, fn=(perf`pmu_add_sys_aliases_iter_fn at
> pmu.c:931), data=0x00007377e7e09b40) at pmu-events.c:5994:23
> frame #10: 0x0000aaaaaaf6cd78
> perf`pmu_events_table__for_each_event(table=0x0000aaaaac299bb0,
> pmu=0x0000000000000000, fn=(perf`pmu_add_sys_aliases_iter_fn at
> pmu.c:931), data=0x00007377e7e09b40) at pmu-events.c:6057:23
> frame #11: 0x0000aaaaaaf6ec44
> perf`pmu_for_each_sys_event(fn=(perf`pmu_add_sys_aliases_iter_fn at
> pmu.c:931), data=0x00007377e7e09b40) at pmu-events.c:6295:27
> frame #12: 0x0000aaaaab41738c
> perf`pmu_add_sys_aliases(pmu=0x00007377e7e09b40) at pmu.c:955:2
> frame #13: 0x0000aaaaab4179fc
> perf`perf_pmu__lookup(pmus=0x0000aaaaac500970, dirfd=34,
> name="arm_cmn_0") at pmu.c:1037:2
> frame #14: 0x0000aaaaab4242d0 perf`perf_pmu__find2(dirfd=34,
> name="arm_cmn_0") at pmus.c:161:9
> frame #15: 0x0000aaaaab421614 perf`pmu_read_sysfs(core_only=false)
> at pmus.c:209:3
> frame #16: 0x0000aaaaab42278c
> perf`perf_pmus__scan_skip_duplicates(pmu=0x0000000000000000) at
> pmus.c:297:3
> frame #17: 0x0000aaaaab422078
> perf`perf_pmus__print_pmu_events(print_cb=0x0000ffffffffec68,
> print_state=0x0000ffffffffecd0) at pmus.c:462:16
> frame #18: 0x0000aaaaab425d9c
> perf`print_events(print_cb=0x0000ffffffffec68,
> print_state=0x0000ffffffffecd0) at print-events.c:409:2
> frame #19: 0x0000aaaaab093ef0 perf`cmd_list(argc=0,
> argv=0x0000fffffffff340) at builtin-list.c:592:3
> frame #20: 0x0000aaaaaaf5b490
> perf`run_builtin(p=0x0000aaaaac4e8220, argc=1,
> argv=0x0000fffffffff340) at perf.c:349:11
> frame #21: 0x0000aaaaaaf5a3e0 perf`handle_internal_command(argc=1,
> argv=0x0000fffffffff340) at perf.c:402:8
> frame #22: 0x0000aaaaaaf5b1a0
> perf`run_argv(argcp=0x0000fffffffff1c8, argv=0x0000fffffffff1c0) at
> perf.c:446:2
> frame #23: 0x0000aaaaaaf59f44 perf`main(argc=1,
> argv=0x0000fffffffff340) at perf.c:562:3
> ```
>
> As such the fix here is incomplete. There may be both sys json events
> (detected by PMU/id name) and CPU json events (detected by CPUID). I'm
> looking into a fix.
Patch sent:
https://lore.kernel.org/lkml/20240511003601.2666907-1-irogers@google.com/
Thanks,
Ian
> Thanks,
> Ian
>
> > --
> > Cheers,
> > Justin (Jia He)
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