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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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