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    SubjectRe: [PATCH 2/5] perf record: Add error message for EMFILE


    On 01/29/2012 01:55 AM, Namhyung Kim wrote:
    > When a user tries to open so many events, perf_event_oen syscall
    > may fail with EMFILE. Provide an advice for that case.
    >
    > Signed-off-by: Namhyung Kim <namhyung@gmail.com>
    > ---
    > tools/perf/builtin-record.c | 4 ++++
    > 1 files changed, 4 insertions(+), 0 deletions(-)
    >
    > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
    > index 32870eef952f..5d3b6794d93b 100644
    > --- a/tools/perf/builtin-record.c
    > +++ b/tools/perf/builtin-record.c
    > @@ -249,6 +249,10 @@ try_again:
    > ui__warning("The %s event is not supported.\n",
    > event_name(pos));
    > exit(EXIT_FAILURE);
    > + } else if (err == EMFILE) {
    > + ui__warning("Too many events are opened.\n"
    > + "Try again after reducing the number of events.\n");
    > + exit(EXIT_FAILURE);
    > }
    >
    > printf("\n");

    It's not just the number of events: an fd is opened for each specified
    event on each specified cpu and for each specified task. See
    __perf_evsel__open(). e.g., the new --uid option on a 16 cpu server can
    hit the limit pretty fast.

    David


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