linux-kernel - Re: [PATCH 2/5] perf record: Add error message for EMFILE

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Message-ID: <4F25EDCC.3010800@gmail.com>
Date:	Mon, 30 Jan 2012 10:09:32 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	David Ahern <dsahern@...il.com>
CC:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] perf record: Add error message for EMFILE

Hello,

2012-01-30 12:28 AM, David Ahern wrote:
> 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@...il.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

Right. How about this then? If it looks OK to you, I'll resend the patch 
for record, top, stat:

	Too many events are opened.
	Try again after reducing the number of events,
	tasks and/or cpus.


Thanks,
Namhyung
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