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perf evlist: Fix error out while applying initial delay and LBR 

'perf record' will error out if both --delay and LBR are applied.

For example:

  # perf record -D 1000 -a -e cycles -j any -- sleep 2
  Error:
  dummy:HG: PMU Hardware doesn't support sampling/overflow-interrupts.
  Try 'perf stat'
  #

A dummy event is added implicitly for initial delay, which has the same
configurations as real sampling events. The dummy event is a software
event. If LBR is configured, perf must error out.

The dummy event will only be used to track PERF_RECORD_MMAP while perf
waits for the initial delay to enable the real events. The BRANCH_STACK
bit can be safely cleared for the dummy event.

After applying the patch:

  # perf record -D 1000 -a -e cycles -j any -- sleep 2
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.054 MB perf.data (828 samples) ]
  #

Reported-by: Sunil K Pandey <sunil.k.pandey@intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1531145722-16404-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
zero-colors
Kan Liang 2018-07-09 07:15:22 -07:00 committed by Arnaldo Carvalho de Melo
parent 61b229ce2c
commit 95035c5e16
1 changed files with 14 additions and 0 deletions
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14
tools/perf/util/evsel.c
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@ -859,6 +859,12 @@ static void apply_config_terms(struct perf_evsel *evsel,
}
}
static bool is_dummy_event(struct perf_evsel *evsel)
{
return (evsel->attr.type == PERF_TYPE_SOFTWARE) &&
(evsel->attr.config == PERF_COUNT_SW_DUMMY);
}
/*
* The enable_on_exec/disabled value strategy:
*
@ -1097,6 +1103,14 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts,
else
perf_evsel__reset_sample_bit(evsel, PERIOD);
}
/*
* For initial_delay, a dummy event is added implicitly.
* The software event will trigger -EOPNOTSUPP error out,
* if BRANCH_STACK bit is set.
*/
if (opts->initial_delay && is_dummy_event(evsel))
perf_evsel__reset_sample_bit(evsel, BRANCH_STACK);
}
static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)