[PATCH v2 2/2] perf bench: Add -t/--threads option to perf bench mem mmap
From: Namhyung Kim
Date: Wed Feb 18 2026 - 19:44:28 EST
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@xxxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxxxxxxxxx>
*/
-#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()
};
--
2.53.0.335.g19a08e0c02-goog