linux-kernel - Re: [PATCH v4 04/10] perf stat: factor out event handling loop into a function

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Date:   Sun, 31 May 2020 20:19:05 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.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 v4 04/10] perf stat: factor out event handling loop into
 a function

On Mon, May 25, 2020 at 05:19:45PM +0300, Alexey Budankov wrote:

SNIP

> @@ -544,12 +598,10 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
>  static int __run_perf_stat(int argc, const char **argv, int run_idx)
>  {
>  	int interval = stat_config.interval;
> -	int times = stat_config.times;
>  	int timeout = stat_config.timeout;
>  	char msg[BUFSIZ];
>  	unsigned long long t0, t1;
>  	struct evsel *counter;
> -	struct timespec ts;
>  	size_t l;
>  	int status = 0;
>  	const bool forks = (argc > 0);
> @@ -558,17 +610,6 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>  	int i, cpu;
>  	bool second_pass = false;
>  
> -	if (interval) {
> -		ts.tv_sec  = interval / USEC_PER_MSEC;
> -		ts.tv_nsec = (interval % USEC_PER_MSEC) * NSEC_PER_MSEC;
> -	} else if (timeout) {
> -		ts.tv_sec  = timeout / USEC_PER_MSEC;
> -		ts.tv_nsec = (timeout % USEC_PER_MSEC) * NSEC_PER_MSEC;
> -	} else {
> -		ts.tv_sec  = 1;
> -		ts.tv_nsec = 0;
> -	}
> -
>  	if (forks) {
>  		if (perf_evlist__prepare_workload(evsel_list, &target, argv, is_pipe,
>  						  workload_exec_failed_signal) < 0) {
> @@ -725,16 +766,9 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>  		perf_evlist__start_workload(evsel_list);
>  		enable_counters();
>  
> -		if (interval || timeout) {
> -			while (!waitpid(child_pid, &status, WNOHANG)) {
> -				nanosleep(&ts, NULL);
> -				if (timeout)
> -					break;
> -				process_interval();
> -				if (interval_count && !(--times))
> -					break;
> -			}
> -		}
> +		if (interval || timeout)
> +			dispatch_events(child_pid, &stat_config);
> +
>  		if (child_pid != -1) {
>  			if (timeout)
>  				kill(child_pid, SIGTERM);
> @@ -751,18 +785,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
>  			psignal(WTERMSIG(status), argv[0]);
>  	} else {
>  		enable_counters();
> -		while (!done) {
> -			nanosleep(&ts, NULL);
> -			if (!is_target_alive(&target, evsel_list->core.threads))
> -				break;
> -			if (timeout)
> -				break;
> -			if (interval) {
> -				process_interval();
> -				if (interval_count && !(--times))
> -					break;
> -			}
> -		}
> +		dispatch_events(-1, &stat_config);

hum, from the discussion we had on v3  I expected more smaller patches
with easy changes, so the change is more transparent and easy to review

as I said before this part really makes me worried and needs to be as clear
as possible.. please introdce the new function first and replace the factored
places separately, also more verbose changelog would help ;-)

thanks,
jirka


>  	}
>  
>  	disable_counters();
> -- 
> 2.24.1
>