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Message-ID: <aHa0QLtTCe1BmkMd@google.com>
Date: Tue, 15 Jul 2025 13:04:16 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ankur Arora <ankur.a.arora@...cle.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org,
akpm@...ux-foundation.org, david@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
mjguzik@...il.com, luto@...nel.org, peterz@...radead.org,
acme@...nel.org, tglx@...utronix.de, willy@...radead.org,
raghavendra.kt@....com, boris.ostrovsky@...cle.com,
konrad.wilk@...cle.com
Subject: Re: [PATCH v5 01/14] perf bench mem: Remove repetition around time
measurement
Hello,
On Wed, Jul 09, 2025 at 05:59:13PM -0700, Ankur Arora wrote:
> We have two copies of each mem benchmark: one using cycles to
> measure time, the second for gettimeofday().
>
> Unify.
>
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
Reviewed-by: Namhyung Kim <namhyung@...nel.org>
Thanks,
Namhyung
> ---
> tools/perf/bench/mem-functions.c | 110 +++++++++++++------------------
> 1 file changed, 46 insertions(+), 64 deletions(-)
>
> diff --git a/tools/perf/bench/mem-functions.c b/tools/perf/bench/mem-functions.c
> index 19d45c377ac1..8599ed96ee1f 100644
> --- a/tools/perf/bench/mem-functions.c
> +++ b/tools/perf/bench/mem-functions.c
> @@ -51,6 +51,11 @@ static const struct option options[] = {
> OPT_END()
> };
>
> +union bench_clock {
> + u64 cycles;
> + struct timeval tv;
> +};
> +
> typedef void *(*memcpy_t)(void *, const void *, size_t);
> typedef void *(*memset_t)(void *, int, size_t);
>
> @@ -91,6 +96,26 @@ static u64 get_cycles(void)
> return clk;
> }
>
> +static void clock_get(union bench_clock *t)
> +{
> + if (use_cycles)
> + t->cycles = get_cycles();
> + else
> + BUG_ON(gettimeofday(&t->tv, NULL));
> +}
> +
> +static union bench_clock clock_diff(union bench_clock *s, union bench_clock *e)
> +{
> + union bench_clock t;
> +
> + if (use_cycles)
> + t.cycles = e->cycles - s->cycles;
> + else
> + timersub(&e->tv, &s->tv, &t.tv);
> +
> + return t;
> +}
> +
> static double timeval2double(struct timeval *ts)
> {
> return (double)ts->tv_sec + (double)ts->tv_usec / (double)USEC_PER_SEC;
> @@ -109,8 +134,7 @@ static double timeval2double(struct timeval *ts)
>
> struct bench_mem_info {
> const struct function *functions;
> - u64 (*do_cycles)(const struct function *r, size_t size, void *src, void *dst);
> - double (*do_gettimeofday)(const struct function *r, size_t size, void *src, void *dst);
> + union bench_clock (*do_op)(const struct function *r, size_t size, void *src, void *dst);
> const char *const *usage;
> bool alloc_src;
> };
> @@ -119,7 +143,7 @@ static void __bench_mem_function(struct bench_mem_info *info, int r_idx, size_t
> {
> const struct function *r = &info->functions[r_idx];
> double result_bps = 0.0;
> - u64 result_cycles = 0;
> + union bench_clock rt = { 0 };
> void *src = NULL, *dst = zalloc(size);
>
> printf("# function '%s' (%s)\n", r->name, r->desc);
> @@ -136,25 +160,23 @@ static void __bench_mem_function(struct bench_mem_info *info, int r_idx, size_t
> if (bench_format == BENCH_FORMAT_DEFAULT)
> printf("# Copying %s bytes ...\n\n", size_str);
>
> - if (use_cycles) {
> - result_cycles = info->do_cycles(r, size, src, dst);
> - } else {
> - result_bps = info->do_gettimeofday(r, size, src, dst);
> - }
> + rt = info->do_op(r, size, src, dst);
>
> switch (bench_format) {
> case BENCH_FORMAT_DEFAULT:
> if (use_cycles) {
> - printf(" %14lf cycles/byte\n", (double)result_cycles/size_total);
> + printf(" %14lf cycles/byte\n", (double)rt.cycles/size_total);
> } else {
> + result_bps = size_total/timeval2double(&rt.tv);
> print_bps(result_bps);
> }
> break;
>
> case BENCH_FORMAT_SIMPLE:
> if (use_cycles) {
> - printf("%lf\n", (double)result_cycles/size_total);
> + printf("%lf\n", (double)rt.cycles/size_total);
> } else {
> + result_bps = size_total/timeval2double(&rt.tv);
> printf("%lf\n", result_bps);
> }
> break;
> @@ -235,38 +257,21 @@ static void memcpy_prefault(memcpy_t fn, size_t size, void *src, void *dst)
> fn(dst, src, size);
> }
>
> -static u64 do_memcpy_cycles(const struct function *r, size_t size, void *src, void *dst)
> +static union bench_clock do_memcpy(const struct function *r, size_t size,
> + void *src, void *dst)
> {
> - u64 cycle_start = 0ULL, cycle_end = 0ULL;
> + union bench_clock start, end;
> memcpy_t fn = r->fn.memcpy;
> int i;
>
> memcpy_prefault(fn, size, src, dst);
>
> - cycle_start = get_cycles();
> + clock_get(&start);
> for (i = 0; i < nr_loops; ++i)
> fn(dst, src, size);
> - cycle_end = get_cycles();
> + clock_get(&end);
>
> - return cycle_end - cycle_start;
> -}
> -
> -static double do_memcpy_gettimeofday(const struct function *r, size_t size, void *src, void *dst)
> -{
> - struct timeval tv_start, tv_end, tv_diff;
> - memcpy_t fn = r->fn.memcpy;
> - int i;
> -
> - memcpy_prefault(fn, size, src, dst);
> -
> - BUG_ON(gettimeofday(&tv_start, NULL));
> - for (i = 0; i < nr_loops; ++i)
> - fn(dst, src, size);
> - BUG_ON(gettimeofday(&tv_end, NULL));
> -
> - timersub(&tv_end, &tv_start, &tv_diff);
> -
> - return (double)(((double)size * nr_loops) / timeval2double(&tv_diff));
> + return clock_diff(&start, &end);
> }
>
> struct function memcpy_functions[] = {
> @@ -292,8 +297,7 @@ int bench_mem_memcpy(int argc, const char **argv)
> {
> struct bench_mem_info info = {
> .functions = memcpy_functions,
> - .do_cycles = do_memcpy_cycles,
> - .do_gettimeofday = do_memcpy_gettimeofday,
> + .do_op = do_memcpy,
> .usage = bench_mem_memcpy_usage,
> .alloc_src = true,
> };
> @@ -301,9 +305,10 @@ int bench_mem_memcpy(int argc, const char **argv)
> return bench_mem_common(argc, argv, &info);
> }
>
> -static u64 do_memset_cycles(const struct function *r, size_t size, void *src __maybe_unused, void *dst)
> +static union bench_clock do_memset(const struct function *r, size_t size,
> + void *src __maybe_unused, void *dst)
> {
> - u64 cycle_start = 0ULL, cycle_end = 0ULL;
> + union bench_clock start, end;
> memset_t fn = r->fn.memset;
> int i;
>
> @@ -313,34 +318,12 @@ static u64 do_memset_cycles(const struct function *r, size_t size, void *src __m
> */
> fn(dst, -1, size);
>
> - cycle_start = get_cycles();
> + clock_get(&start);
> for (i = 0; i < nr_loops; ++i)
> fn(dst, i, size);
> - cycle_end = get_cycles();
> + clock_get(&end);
>
> - return cycle_end - cycle_start;
> -}
> -
> -static double do_memset_gettimeofday(const struct function *r, size_t size, void *src __maybe_unused, void *dst)
> -{
> - struct timeval tv_start, tv_end, tv_diff;
> - memset_t fn = r->fn.memset;
> - int i;
> -
> - /*
> - * We prefault the freshly allocated memory range here,
> - * to not measure page fault overhead:
> - */
> - fn(dst, -1, size);
> -
> - BUG_ON(gettimeofday(&tv_start, NULL));
> - for (i = 0; i < nr_loops; ++i)
> - fn(dst, i, size);
> - BUG_ON(gettimeofday(&tv_end, NULL));
> -
> - timersub(&tv_end, &tv_start, &tv_diff);
> -
> - return (double)(((double)size * nr_loops) / timeval2double(&tv_diff));
> + return clock_diff(&start, &end);
> }
>
> static const char * const bench_mem_memset_usage[] = {
> @@ -366,8 +349,7 @@ int bench_mem_memset(int argc, const char **argv)
> {
> struct bench_mem_info info = {
> .functions = memset_functions,
> - .do_cycles = do_memset_cycles,
> - .do_gettimeofday = do_memset_gettimeofday,
> + .do_op = do_memset,
> .usage = bench_mem_memset_usage,
> };
>
> --
> 2.43.5
>
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