Re: [PATCH v3 1/3] perf evsel: Improve the evsel__open_strerror for EBUSY

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Jan 06, 2025 at 01:59:25PM -0800, Ian Rogers wrote:
> On Tue, Nov 5, 2024 at 4:30 PM Chun-Tse Shao <ctshao@google.com> wrote:
> >
> > From: Ian Rogers <irogers@google.com>
> >
> > The existing EBUSY strerror message is:
> >
> >   The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (intel_bts//).
> >   "dmesg | grep -i perf" may provide additional information.
> >
> > The dmesg won't be useful. What is more useful is knowing what
> > processes are potentially using the PMU, which some procfs scanning can
> > reveal. When parallel testing tests/shell/stat_all_pmu.sh this yields:
> >
> >   Testing intel_bts//
> >   Error:
> >   The PMU intel_bts counters are busy and in use by another process.
> >   Possible processes:
> >   2585882 perf list
> >   2585902 perf list -j -o /tmp/__perf_test.list_output.json.KF9MY
> >   2585904 perf list
> >   2585911 perf record -e task-clock --filter period > 1 -o /dev/null --quiet true
> >   2585912 perf list
> >   2585915 perf list
> >   2586042 /tmp/perf/perf record -asdg -e cpu-clock -o /tmp/perftool-testsuite_report.dIF/perf_report/perf.data -- sleep 2
> >   2589078 perf record -g -e task-clock:u -o - perf test -w noploop
> >   2589148 /tmp/perf/perf record --control=fifo:control,ack -e cpu-clock -m 1 sleep 10
> >   2589379 perf --buildid-dir /tmp/perf.debug.Umx record --buildid-all -o /tmp/perf.data.YBm /tmp/perf.ex.MD5.ZQW
> >   2589568 perf record -o /tmp/__perf_test.program.mtcZH/perf.data --branch-filter any,save_type,u -- perf test -w brstack
> >   2589649 perf record --per-thread -o /tmp/__perf_test.perf.data.5d3dc perf test -w thloop
> >   2589898 perf record -o /tmp/perf-test-script.BX2b27Dcnj/pp-perf.data --sample-cpu uname
> >
> > Which gets a little closer to finding the issue.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> 
> Ping.

Thanks for the ping, great stuff, testing the first patch:

Committer testing:

  root@number:~#
  root@number:~# grep -m1 "model name" /proc/cpuinfo
  model name    : Intel(R) Core(TM) i7-14700K
  root@number:~#

Before:

  root@number:~# perf stat -e intel_bts// &
  [1] 197954
  root@number:~# perf test "perf all PMU test"
  124: perf all PMU test                                               : FAILED!
  root@number:~# perf test -v "perf all PMU test" |& tail
  Testing i915/vecs0-busy/
  Testing i915/vecs0-sema/
  Testing i915/vecs0-wait/
  Testing intel_bts//
  Unexpected signal in main
  Error:
  The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (intel_bts//).
  "dmesg | grep -i perf" may provide additional information.
  ---- end(-1) ----
  124: perf all PMU test                                               : FAILED!
  root@number:~#

After:

  root@number:~# perf stat -e intel_bts// &
  [1] 200195
  root@number:~# perf test "perf all PMU test"
  123: perf all PMU test                                               : FAILED!
  root@number:~# perf test -v "perf all PMU test" |& tail
  Testing i915/vecs0-wait/
  Testing intel_bts//
  Unexpected signal in main
  Error:
  The PMU intel_bts counters are busy and in use by another process.
  Possible processes:
  200195 perf stat -e intel_bts//
  2319766 /root/bin/perf top --stdio
  ---- end(-1) ----
  123: perf all PMU test                                               : FAILED!
  root@number:~#