Date:   Thu, 24 Aug 2017 16:39:02 -0400
From:   Aaron Lindsay <alindsay@...eaurora.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>
Cc:     Digant Desai <digantd@...eaurora.org>, timur@...eaurora.org
Subject: Re: [PATCH] perf stat: Add event-interval-print option

Does anyone have any feedback on this patch or the idea in general?

Also, (for our bookkeeping - not trying to rush things) is there any
chance this will still make it in for the 4.14 merge window, or is it
4.15 material at the earliest?

-Aaron

On Aug 16 11:08, Aaron Lindsay wrote:
> This allows for printing counts at regular intervals based on <n>
> instances of an arbitrary event (currently the first event provided).
> 
> This can be useful when comparing `perf stat` runs of fixed-work
> workloads. For instance, you may want to compare interval-by-interval
> stats between two runs based on instruction count rather than time
> intervals to ensure the same sections of the userspace component of code
> are aligned when comparing them (which wouldn't necessarily be the case
> if the kernel was misbehaving in only one of the compared runs).
> 
> Signed-off-by: Aaron Lindsay <alindsay@...eaurora.org>
> Tested-by: Digant Desai <digantd@...eaurora.org>
> ---
>  tools/perf/builtin-stat.c | 114 ++++++++++++++++++++++++++++++++++++++++++----
>  tools/perf/util/evsel.h   |   1 +
>  tools/perf/util/stat.h    |   1 +
>  3 files changed, 107 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 48ac53b..e400cd3 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -71,7 +71,9 @@
>  #include <api/fs/fs.h>
>  #include <errno.h>
>  #include <signal.h>
> +#include <poll.h>
>  #include <stdlib.h>
> +#include <sys/mman.h>
>  #include <sys/prctl.h>
>  #include <inttypes.h>
>  #include <locale.h>
> @@ -224,7 +226,8 @@ static int create_perf_stat_counter(struct perf_evsel *evsel)
>  	 * Some events get initialized with sample_(period/type) set,
>  	 * like tracepoints. Clear it up for counting.
>  	 */
> -	attr->sample_period = 0;
> +	if (!evsel->event_interval)
> +		attr->sample_period = 0;
>  
>  	/*
>  	 * But set sample_type to PERF_SAMPLE_IDENTIFIER, which should be harmless
> @@ -562,6 +565,7 @@ static int store_counter_ids(struct perf_evsel *counter)
>  static int __run_perf_stat(int argc, const char **argv)
>  {
>  	int interval = stat_config.interval;
> +	int event_interval = stat_config.event_interval;
>  	char msg[BUFSIZ];
>  	unsigned long long t0, t1;
>  	struct perf_evsel *counter;
> @@ -571,6 +575,9 @@ static int __run_perf_stat(int argc, const char **argv)
>  	const bool forks = (argc > 0);
>  	bool is_pipe = STAT_RECORD ? perf_stat.file.is_pipe : false;
>  	struct perf_evsel_config_term *err_term;
> +	bool first_counter = true;
> +
> +	struct pollfd interval_pollfd = {.fd = 0, .events = POLLIN};
>  
>  	if (interval) {
>  		ts.tv_sec  = interval / USEC_PER_MSEC;
> @@ -594,6 +601,32 @@ static int __run_perf_stat(int argc, const char **argv)
>  
>  	evlist__for_each_entry(evsel_list, counter) {
>  try_again:
> +		if (first_counter && event_interval) {
> +			/*
> +			 * Setup this counter as an event interval by pinning
> +			 * it, setting it to sample based on the user-specified
> +			 * period, and to return from polling on expiration
> +			 * (i.e. when any data is written to the buffer)
> +			 */
> +			int nthreads = thread_map__nr(evsel_list->threads);
> +			int ncpus = perf_evsel__nr_cpus(counter);
> +
> +			if (nthreads > 1 || ncpus > 1) {
> +				perror("Failed to setup event-interval-print "
> +				       "because the event has more than one "
> +				       "CPU or thread.");
> +				return -1;
> +			}
> +
> +			counter->attr.pinned = 1;
> +			counter->attr.watermark = 1;
> +			counter->attr.wakeup_watermark = 1;
> +			counter->attr.sample_period = event_interval;
> +			counter->attr.freq = 0;
> +			counter->event_interval = true;
> +
> +			pr_debug2("Polling on %s\n", perf_evsel__name(counter));
> +		}
>  		if (create_perf_stat_counter(counter) < 0) {
>  			/*
>  			 * PPC returns ENXIO for HW counters until 2.6.37
> @@ -633,6 +666,33 @@ static int __run_perf_stat(int argc, const char **argv)
>  
>  		if (STAT_RECORD && store_counter_ids(counter))
>  			return -1;
> +
> +		if (first_counter && event_interval) {
> +			void *m;
> +
> +			interval_pollfd.fd =
> +				*(int *)xyarray__entry(counter->fd, 0, 0);
> +
> +			/*
> +			 * Do not set PROT_WRITE since the kernel will stop
> +			 * writing to the mmap buffer when it fills if
> +			 * data_tail is not set. Map 2 pages since the kernel
> +			 * requires the first for metadata.
> +			 */
> +			m = mmap(NULL, 2 * getpagesize(), PROT_READ, MAP_SHARED,
> +					interval_pollfd.fd, 0);
> +			if (m == (void *) -1) {
> +				perror("Failed to mmap print-event-interval "
> +				       "fd");
> +				return -1;
> +			}
> +		}
> +
> +		first_counter = false;
> +	}
> +	if (event_interval && !interval_pollfd.fd) {
> +		perror("Failed to initialize print-event-interval fd");
> +		return -1;
>  	}
>  
>  	if (perf_evlist__apply_filters(evsel_list, &counter)) {
> @@ -677,7 +737,18 @@ static int __run_perf_stat(int argc, const char **argv)
>  		perf_evlist__start_workload(evsel_list);
>  		enable_counters();
>  
> -		if (interval) {
> +		if (event_interval) {
> +			while (!waitpid(child_pid, &status, WNOHANG)) {
> +				/*
> +				 * Wait for the event to expire for at most 1
> +				 * second
> +				 */
> +				if (poll(&interval_pollfd, 1, 1000) > 0) {
> +					if (interval_pollfd.revents & (POLLIN))
> +						process_interval();
> +				}
> +			}
> +		} else if (interval) {
>  			while (!waitpid(child_pid, &status, WNOHANG)) {
>  				nanosleep(&ts, NULL);
>  				process_interval();
> @@ -696,9 +767,20 @@ static int __run_perf_stat(int argc, const char **argv)
>  	} else {
>  		enable_counters();
>  		while (!done) {
> -			nanosleep(&ts, NULL);
> -			if (interval)
> -				process_interval();
> +			if (event_interval) {
> +				/*
> +				 * Wait for the event to expire for at most 1
> +				 * second
> +				 */
> +				if (poll(&interval_pollfd, 1, 1000) > 0) {
> +					if (interval_pollfd.revents & (POLLIN))
> +						process_interval();
> +				}
> +			} else {
> +				nanosleep(&ts, NULL);
> +				if (interval)
> +					process_interval();
> +			}
>  		}
>  	}
>  
> @@ -1614,7 +1696,7 @@ static void print_footer(void)
>  
>  static void print_counters(struct timespec *ts, int argc, const char **argv)
>  {
> -	int interval = stat_config.interval;
> +	int interval = stat_config.interval || stat_config.event_interval;
>  	struct perf_evsel *counter;
>  	char buf[64], *prefix = NULL;
>  
> @@ -1781,6 +1863,8 @@ static int enable_metric_only(const struct option *opt __maybe_unused,
>  			"command to run after to the measured command"),
>  	OPT_UINTEGER('I', "interval-print", &stat_config.interval,
>  		    "print counts at regular interval in ms (>= 10)"),
> +	OPT_UINTEGER('E', "event-interval-print", &stat_config.event_interval,
> +		    "print counts every <n> of the first event specified"),
>  	OPT_SET_UINT(0, "per-socket", &stat_config.aggr_mode,
>  		     "aggregate counts per processor socket", AGGR_SOCKET),
>  	OPT_SET_UINT(0, "per-core", &stat_config.aggr_mode,
> @@ -2546,7 +2630,7 @@ int cmd_stat(int argc, const char **argv)
>  	int status = -EINVAL, run_idx;
>  	const char *mode;
>  	FILE *output = stderr;
> -	unsigned int interval;
> +	unsigned int interval, event_interval;
>  	const char * const stat_subcommands[] = { "record", "report" };
>  
>  	setlocale(LC_ALL, "");
> @@ -2577,6 +2661,7 @@ int cmd_stat(int argc, const char **argv)
>  		return __cmd_report(argc, argv);
>  
>  	interval = stat_config.interval;
> +	event_interval = stat_config.event_interval;
>  
>  	/*
>  	 * For record command the -o is already taken care of.
> @@ -2704,6 +2789,17 @@ int cmd_stat(int argc, const char **argv)
>  	if (stat_config.aggr_mode == AGGR_THREAD)
>  		thread_map__read_comms(evsel_list->threads);
>  
> +	if (interval && event_interval) {
> +		pr_err("interval-print and event-interval-print options "
> +			"cannot be used together\n");
> +		goto out;
> +	}
> +
> +	if (event_interval && !no_inherit) {
> +		pr_err("The event-interval-print option requires no-inherit\n");
> +		goto out;
> +	}
> +
>  	if (interval && interval < 100) {
>  		if (interval < 10) {
>  			pr_err("print interval must be >= 10ms\n");
> @@ -2715,7 +2811,7 @@ int cmd_stat(int argc, const char **argv)
>  				   "Please proceed with caution.\n");
>  	}
>  
> -	if (perf_evlist__alloc_stats(evsel_list, interval))
> +	if (perf_evlist__alloc_stats(evsel_list, interval || event_interval))
>  		goto out;
>  
>  	if (perf_stat_init_aggr_mode())
> @@ -2747,7 +2843,7 @@ int cmd_stat(int argc, const char **argv)
>  		}
>  	}
>  
> -	if (!forever && status != -1 && !interval)
> +	if (!forever && status != -1 && !interval && !event_interval)
>  		print_counters(NULL, argc, argv);
>  
>  	if (STAT_RECORD) {
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index d101695..44a65e6 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -121,6 +121,7 @@ struct perf_evsel {
>  	bool			per_pkg;
>  	bool			precise_max;
>  	bool			ignore_missing_thread;
> +	bool			event_interval;
>  	/* parse modifier helper */
>  	int			exclude_GH;
>  	int			nr_members;
> diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> index 7522bf1..db4dda4 100644
> --- a/tools/perf/util/stat.h
> +++ b/tools/perf/util/stat.h
> @@ -46,6 +46,7 @@ struct perf_stat_config {
>  	bool		scale;
>  	FILE		*output;
>  	unsigned int	interval;
> +	unsigned int	event_interval;
>  };
>  
>  void update_stats(struct stats *stats, u64 val);
> -- 
> Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
> Qualcomm Technologies, Inc. is a member of the
> Code Aurora Forum, a Linux Foundation Collaborative Project.
> 

-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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