Re: [PATCH v2 2/2] perf bench: Add -t/--threads option to perf bench mem mmap

[Ankur Arora <ankur.a.arora@oracle.com>]

Namhyung Kim <namhyung@kernel.org> writes:

> So that it can measure overhead of mmap_lock and/or per-VMA lock
> contention.
>
>   $ perf bench mem mmap -f demand -l 1000 -t 1
>   # Running 'mem/mmap' benchmark:
>   # function 'demand' (Demand loaded mmap())
>   # Copying 1MB bytes ...
>
>          2.786858 GB/sec
>
>   $ perf bench mem mmap -f demand -l 1000 -t 2
>   # Running 'mem/mmap' benchmark:
>   # function 'demand' (Demand loaded mmap())
>   # Copying 1MB bytes ...
>
>          1.624468 GB/sec/thread   ( +-   0.30% )
>
>   $ perf bench mem mmap -f demand -l 1000 -t 3
>   # Running 'mem/mmap' benchmark:
>   # function 'demand' (Demand loaded mmap())
>   # Copying 1MB bytes ...
>
>          1.493068 GB/sec/thread   ( +-   0.15% )
>
>   $ perf bench mem mmap -f demand -l 1000 -t 4
>   # Running 'mem/mmap' benchmark:
>   # function 'demand' (Demand loaded mmap())
>   # Copying 1MB bytes ...
>
>          1.006087 GB/sec/thread   ( +-   0.41% )
>
> Cc: Ankur Arora <ankur.a.arora@oracle.com>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Reviewed-by: Ankur Arora <ankur.a.arora@oracle.com>

> ---
> v2)
>  * correct timeval2double calculation
>  * add "/thread" notation when -t > 1  (James)
>  * add stddev when -t > 1  (Ankur)
>
>  tools/perf/Documentation/perf-bench.txt |   4 +
>  tools/perf/bench/mem-functions.c        | 109 +++++++++++++++++++-----
>  2 files changed, 92 insertions(+), 21 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documentation/perf-bench.txt
> index 1160224cb718392d..c5913cf59c988421 100644
> --- a/tools/perf/Documentation/perf-bench.txt
> +++ b/tools/perf/Documentation/perf-bench.txt
> @@ -274,6 +274,10 @@ Repeat mmap() invocation this number of times.
>  --cycles::
>  Use perf's cpu-cycles event instead of gettimeofday syscall.
>
> +-t::
> +--threads=<NUM>::
> +Create multiple threads to call mmap/munmap concurrently.
> +
>  SUITES FOR 'numa'
>  ~~~~~~~~~~~~~~~~~
>  *mem*::
> diff --git a/tools/perf/bench/mem-functions.c b/tools/perf/bench/mem-functions.c
> index 676c8d18f4c2e259..8e04ae69f8a85c5e 100644
> --- a/tools/perf/bench/mem-functions.c
> +++ b/tools/perf/bench/mem-functions.c
> @@ -7,13 +7,14 @@
>   * Written by Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
>   */
>
> -#include "debug.h"
> +#include "bench.h"
>  #include "../perf-sys.h"
>  #include <subcmd/parse-options.h>
> -#include "../util/header.h"
> -#include "../util/cloexec.h"
> -#include "../util/string2.h"
> -#include "bench.h"
> +#include "util/cloexec.h"
> +#include "util/debug.h"
> +#include "util/header.h"
> +#include "util/stat.h"
> +#include "util/string2.h"
>  #include "mem-memcpy-arch.h"
>  #include "mem-memset-arch.h"
>
> @@ -26,6 +27,7 @@
>  #include <errno.h>
>  #include <linux/time64.h>
>  #include <linux/log2.h>
> +#include <pthread.h>
>
>  #define K 1024
>
> @@ -41,6 +43,7 @@ static unsigned int	nr_loops	= 1;
>  static bool		use_cycles;
>  static int		cycles_fd;
>  static unsigned int	seed;
> +static unsigned int	nr_threads	= 1;
>
>  static const struct option bench_common_options[] = {
>  	OPT_STRING('s', "size", &size_str, "1MB",
> @@ -121,6 +124,8 @@ static struct perf_event_attr cycle_attr = {
>  	.config		= PERF_COUNT_HW_CPU_CYCLES
>  };
>
> +static struct stats stats;
> +
>  static int init_cycles(void)
>  {
>  	cycles_fd = sys_perf_event_open(&cycle_attr, getpid(), -1, -1, perf_event_open_cloexec_flag());
> @@ -174,18 +179,18 @@ static void clock_accum(union bench_clock *a, union bench_clock *b)
>
>  static double timeval2double(struct timeval *ts)
>  {
> -	return (double)ts->tv_sec + (double)ts->tv_usec / (double)USEC_PER_SEC;
> +	return ((double)ts->tv_sec + (double)ts->tv_usec / (double)USEC_PER_SEC) / nr_threads;
>  }
>
>  #define print_bps(x) do {						\
>  		if (x < K)						\
> -			printf(" %14lf bytes/sec\n", x);		\
> +			printf(" %14lf bytes/sec", x);			\
>  		else if (x < K * K)					\
> -			printf(" %14lfd KB/sec\n", x / K);		\
> +			printf(" %14lfd KB/sec", x / K);		\
>  		else if (x < K * K * K)					\
> -			printf(" %14lf MB/sec\n", x / K / K);		\
> +			printf(" %14lf MB/sec", x / K / K);		\
>  		else							\
> -			printf(" %14lf GB/sec\n", x / K / K / K);	\
> +			printf(" %14lf GB/sec", x / K / K / K);	\
>  	} while (0)
>
>  static void __bench_mem_function(struct bench_mem_info *info, struct bench_params *p,
> @@ -197,6 +202,7 @@ static void __bench_mem_function(struct bench_mem_info *info, struct bench_param
>  	void *src = NULL, *dst = NULL;
>
>  	memset(&rt, 0, sizeof(rt));
> +	init_stats(&stats);
>  	printf("# function '%s' (%s)\n", r->name, r->desc);
>
>  	if (r->fn.init && r->fn.init(info, p, &src, &dst))
> @@ -211,11 +217,16 @@ static void __bench_mem_function(struct bench_mem_info *info, struct bench_param
>  	switch (bench_format) {
>  	case BENCH_FORMAT_DEFAULT:
>  		if (use_cycles) {
> -			printf(" %14lf cycles/byte\n", (double)rt.cycles/(double)p->size_total);
> +			printf(" %14lf cycles/byte", (double)rt.cycles/(double)p->size_total);
>  		} else {
>  			result_bps = (double)p->size_total/timeval2double(&rt.tv);
>  			print_bps(result_bps);
>  		}
> +		if (nr_threads > 1) {
> +			printf("/thread\t( +- %6.2f%% )",
> +			       rel_stddev_stats(stddev_stats(&stats), avg_stats(&stats)));
> +		}
> +		printf("\n");
>  		break;
>
>  	case BENCH_FORMAT_SIMPLE:
> @@ -495,16 +506,27 @@ static void mmap_page_touch(void *dst, size_t size, unsigned int page_shift, boo
>  	}
>  }
>
> -static int do_mmap(const struct function *r, struct bench_params *p,
> -		  void *src __maybe_unused, void *dst __maybe_unused,
> -		  union bench_clock *accum)
> +struct mmap_data {
> +	pthread_t id;
> +	const struct function *func;
> +	struct bench_params *params;
> +	union bench_clock result;
> +	unsigned int seed;
> +	int error;
> +};
> +
> +static void *do_mmap_thread(void *arg)
>  {
> +	struct mmap_data *data = arg;
> +	const struct function *r = data->func;
> +	struct bench_params *p = data->params;
>  	union bench_clock start, end, diff;
>  	mmap_op_t fn = r->fn.mmap_op;
>  	bool populate = strcmp(r->name, "populate") == 0;
> +	void *dst;
>
> -	if (p->seed)
> -		srand(p->seed);
> +	if (data->seed)
> +		srand(data->seed);
>
>  	for (unsigned int i = 0; i < p->nr_loops; i++) {
>  		clock_get(&start);
> @@ -515,16 +537,59 @@ static int do_mmap(const struct function *r, struct bench_params *p,
>  		fn(dst, p->size, p->page_shift, p->seed);
>  		clock_get(&end);
>  		diff = clock_diff(&start, &end);
> -		clock_accum(accum, &diff);
> +		clock_accum(&data->result, &diff);
>
>  		bench_munmap(dst, p->size);
>  	}
>
> -	return 0;
> +	return data;
>  out:
> -	printf("# Memory allocation failed - maybe size (%s) %s?\n", size_str,
> -			p->page_shift != PAGE_SHIFT_4KB ? "has insufficient hugepages" : "is too large");
> -	return -1;
> +	data->error = -ENOMEM;
> +	return NULL;
> +}
> +
> +static int do_mmap(const struct function *r, struct bench_params *p,
> +		  void *src __maybe_unused, void *dst __maybe_unused,
> +		  union bench_clock *accum)
> +{
> +	struct mmap_data *data;
> +	int error = 0;
> +
> +	data = calloc(nr_threads, sizeof(*data));
> +	if (!data) {
> +		printf("# Failed to allocate thread resources\n");
> +		return -1;
> +	}
> +
> +	for (unsigned int i = 0; i < nr_threads; i++) {
> +		data[i].func = r;
> +		data[i].params = p;
> +		if (p->seed)
> +			data[i].seed = p->seed + i;
> +
> +		if (pthread_create(&data[i].id, NULL, do_mmap_thread, &data[i]) < 0)
> +			data[i].error = -errno;
> +	}
> +
> +	for (unsigned int i = 0; i < nr_threads; i++) {
> +		union bench_clock *t = &data[i].result;
> +
> +		pthread_join(data[i].id, NULL);
> +
> +		clock_accum(accum, t);
> +		if (use_cycles)
> +			update_stats(&stats, t->cycles);
> +		else
> +			update_stats(&stats, t->tv.tv_sec * 1e6 + t->tv.tv_usec);
> +		error |= data[i].error;
> +	}
> +	free(data);
> +
> +	if (error) {
> +		printf("# Memory allocation failed - maybe size (%s) %s?\n", size_str,
> +		       p->page_shift != PAGE_SHIFT_4KB ? "has insufficient hugepages" : "is too large");
> +	}
> +	return error ? -1 : 0;
>  }
>
>  static const char * const bench_mem_mmap_usage[] = {
> @@ -549,6 +614,8 @@ int bench_mem_mmap(int argc, const char **argv)
>  	static const struct option bench_mmap_options[] = {
>  		OPT_UINTEGER('r', "randomize", &seed,
>  			    "Seed to randomize page access offset."),
> +		OPT_UINTEGER('t', "threads", &nr_threads,
> +			    "Number of threads to run concurrently (default: 1)."),
>  		OPT_PARENT(bench_common_options),
>  		OPT_END()
>  	};


--
ankur