linux-kernel - Re: [PATCH v9 09/15] perf stat: factor out event handling loop into dispatch

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Date:   Mon, 6 Jul 2020 16:07:54 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 09/15] perf stat: factor out event handling loop into
 dispatch_events()


On 06.07.2020 15:27, Jiri Olsa wrote:
> On Fri, Jul 03, 2020 at 10:46:15AM +0300, Alexey Budankov wrote:
>>
>> Consolidate event dispatching loops for fork, attach and system
>> wide monitoring use cases into common dispatch_events() function.
>>
>> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
>> ---
>>  tools/perf/builtin-stat.c | 42 +++++++++++++++++++++++++--------------
>>  1 file changed, 27 insertions(+), 15 deletions(-)
>>
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index 3e11f854ffc8..723f1fe27d63 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -550,6 +550,30 @@ static bool is_target_alive(struct target *_target,
>>  	return false;
>>  }
>>  
>> +static int dispatch_events(bool forks, int timeout, int interval, int *times, struct timespec *ts)
>> +{
>> +	bool stop = false;
>> +	int child_exited = 0, status = 0;
>> +
>> +	while (1) {
>> +		if (forks)
>> +			child_exited = waitpid(child_pid, &status, WNOHANG);
>> +		else
>> +			child_exited = !is_target_alive(&target, evsel_list->core.threads) ? 1 : 0;
>> +
>> +		if (done || stop || child_exited)
>> +			break;
> 
> can (done || stop) be in the while condition and
> we'd check just child_exited in here?
> 
>> +
>> +		nanosleep(ts, NULL);
>> +		if (timeout)
>> +			stop = true;
> 
> can we just break out in here? like the original code?
> I don't think we need the extra iteration
> 
>> +		else
>> +			stop = handle_interval(interval, times);
> 
> same here..?

Accepted. In v10.

Alexey