[PATCH 3/8] perf bench futex: Use the whole timeval for elapsed times
From: Michal Pluta
Date: Sat Sep 26 2026 - 15:05:13 EST
Several futex benchmarks read only one field of the struct timeval that
timersub() produces, so part of the elapsed time is lost.
'futex wake', 'futex wake-parallel' and 'futex requeue' print tv_usec,
so a run that takes 1.5 s is shown as 500 ms. 'futex hash' and 'futex
lock-pi' divide their operation count by tv_sec, which overstates the
throughput when a run is stopped early, and gives 0 if that happens
within the first second. Their "total secs" is truncated in the same
way.
Use the whole timeval and print "total secs" with two decimals. With
--runtime=0 the rate is now computed over the time that actually
elapsed, instead of showing 0.
Fixes: 27db78307481 ("perf bench: Add futex-wake microbenchmark")
Fixes: 0fb298cf95c0 ("perf bench: Add futex-requeue microbenchmark")
Fixes: a043971141f1 ("perf bench: Add futex-hash microbenchmark")
Fixes: d2f3f5d2e9ca ("perf bench futex: Add lock_pi stresser")
Fixes: d65817b4e707 ("perf bench futex: Support parallel waker threads")
Assisted-by: LLM
Signed-off-by: Michal Pluta <michalpl2003@xxxxxxxxx>
---
tools/perf/bench/futex-hash.c | 12 ++++++++----
tools/perf/bench/futex-lock-pi.c | 12 ++++++++----
tools/perf/bench/futex-requeue.c | 8 +++++---
tools/perf/bench/futex-wake-parallel.c | 8 ++++++--
tools/perf/bench/futex-wake.c | 6 ++++--
5 files changed, 31 insertions(+), 15 deletions(-)
diff --git a/tools/perf/bench/futex-hash.c b/tools/perf/bench/futex-hash.c
index 7e29f04da744..32b88df8ee6d 100644
--- a/tools/perf/bench/futex-hash.c
+++ b/tools/perf/bench/futex-hash.c
@@ -18,6 +18,7 @@
#include <stdlib.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
+#include <linux/time64.h>
#include <linux/zalloc.h>
#include <sys/time.h>
#include <sys/mman.h>
@@ -118,18 +119,19 @@ static void print_summary(void)
unsigned long avg = avg_stats(&throughput_stats);
double stddev = stddev_stats(&throughput_stats);
- printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
+ printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %.2f\n",
!params.silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
- (int)bench__runtime.tv_sec);
+ bench__runtime.tv_sec + bench__runtime.tv_usec / (double)USEC_PER_SEC);
futex_print_nbuckets(¶ms);
}
int bench_futex_hash(int argc, const char **argv)
{
int ret = 0;
cpu_set_t *cpuset;
struct sigaction act;
unsigned int i;
+ u64 runtime_us;
pthread_attr_t thread_attr;
struct worker *worker = NULL;
struct perf_cpu_map *cpu;
@@ -229,9 +231,11 @@ int bench_futex_hash(int argc, const char **argv)
cond_destroy(&thread_worker);
mutex_destroy(&thread_lock);
+ runtime_us = (u64)bench__runtime.tv_sec * USEC_PER_SEC + bench__runtime.tv_usec;
+
for (i = 0; i < params.nthreads; i++) {
- unsigned long t = bench__runtime.tv_sec > 0 ?
- worker[i].ops / bench__runtime.tv_sec : 0;
+ unsigned long t = runtime_us ?
+ (u64)worker[i].ops * USEC_PER_SEC / runtime_us : 0;
update_stats(&throughput_stats, t);
if (!params.silent) {
if (params.nfutexes == 1)
diff --git a/tools/perf/bench/futex-lock-pi.c b/tools/perf/bench/futex-lock-pi.c
index 40640b674427..7190f5102e09 100644
--- a/tools/perf/bench/futex-lock-pi.c
+++ b/tools/perf/bench/futex-lock-pi.c
@@ -13,6 +13,7 @@
#include <subcmd/parse-options.h>
#include <linux/compiler.h>
#include <linux/kernel.h>
+#include <linux/time64.h>
#include <linux/zalloc.h>
#include <errno.h>
#include <perf/cpumap.h>
@@ -66,9 +67,9 @@ static void print_summary(void)
unsigned long avg = avg_stats(&throughput_stats);
double stddev = stddev_stats(&throughput_stats);
- printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %d\n",
+ printf("%sAveraged %ld operations/sec (+- %.2f%%), total secs = %.2f\n",
!params.silent ? "\n" : "", avg, rel_stddev_stats(stddev, avg),
- (int)bench__runtime.tv_sec);
+ bench__runtime.tv_sec + bench__runtime.tv_usec / (double)USEC_PER_SEC);
futex_print_nbuckets(¶ms);
}
@@ -168,6 +169,7 @@ int bench_futex_lock_pi(int argc, const char **argv)
{
int ret = 0;
unsigned int i;
+ u64 runtime_us;
struct sigaction act;
struct perf_cpu_map *cpu;
@@ -233,9 +235,11 @@ int bench_futex_lock_pi(int argc, const char **argv)
cond_destroy(&thread_worker);
mutex_destroy(&thread_lock);
+ runtime_us = (u64)bench__runtime.tv_sec * USEC_PER_SEC + bench__runtime.tv_usec;
+
for (i = 0; i < params.nthreads; i++) {
- unsigned long t = bench__runtime.tv_sec > 0 ?
- worker[i].ops / bench__runtime.tv_sec : 0;
+ unsigned long t = runtime_us ?
+ (u64)worker[i].ops * USEC_PER_SEC / runtime_us : 0;
update_stats(&throughput_stats, t);
if (!params.silent)
diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c
index 0748b0fd689e..5d4708f40c60 100644
--- a/tools/perf/bench/futex-requeue.c
+++ b/tools/perf/bench/futex-requeue.c
@@ -223,6 +223,7 @@ int bench_futex_requeue(int argc, const char **argv)
for (j = 0; j < bench_repeat && !done; j++) {
unsigned int nrequeued = 0, wakeups = 0;
struct timeval start, end, runtime;
+ u64 runtime_us;
/* create, launch & block all threads */
block_threads(worker, cpu);
@@ -267,23 +268,24 @@ int bench_futex_requeue(int argc, const char **argv)
gettimeofday(&end, NULL);
timersub(&end, &start, &runtime);
+ runtime_us = (u64)runtime.tv_sec * USEC_PER_SEC + runtime.tv_usec;
update_stats(&requeued_stats, nrequeued);
- update_stats(&requeuetime_stats, runtime.tv_usec);
+ update_stats(&requeuetime_stats, runtime_us);
if (!params.silent) {
if (!params.pi)
printf("[Run %d]: Requeued %d of %d threads in "
"%.4f ms\n", j + 1, nrequeued,
params.nthreads,
- runtime.tv_usec / (double)USEC_PER_MSEC);
+ runtime_us / (double)USEC_PER_MSEC);
else {
nrequeued -= wakeups;
printf("[Run %d]: Awoke and Requeued (%d+%d) of "
"%d threads in %.4f ms\n",
j + 1, wakeups, nrequeued,
params.nthreads,
- runtime.tv_usec / (double)USEC_PER_MSEC);
+ runtime_us / (double)USEC_PER_MSEC);
}
}
diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c
index a089d8ee4b02..fa70b7d4b473 100644
--- a/tools/perf/bench/futex-wake-parallel.c
+++ b/tools/perf/bench/futex-wake-parallel.c
@@ -192,7 +192,9 @@ static void print_run(struct thread_data *waking_worker, unsigned int run_num)
init_stats(&__waketime_stats);
for (i = 0; i < params.nwakes; i++) {
- update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
+ update_stats(&__waketime_stats,
+ (u64)waking_worker[i].runtime.tv_sec * USEC_PER_SEC +
+ waking_worker[i].runtime.tv_usec);
update_stats(&__wakeup_stats, waking_worker[i].nwoken);
}
@@ -229,7 +231,9 @@ static void do_run_stats(struct thread_data *waking_worker)
unsigned int i;
for (i = 0; i < params.nwakes; i++) {
- update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
+ update_stats(&waketime_stats,
+ (u64)waking_worker[i].runtime.tv_sec * USEC_PER_SEC +
+ waking_worker[i].runtime.tv_usec);
update_stats(&wakeup_stats, waking_worker[i].nwoken);
}
diff --git a/tools/perf/bench/futex-wake.c b/tools/perf/bench/futex-wake.c
index 58427bb55c03..12a75be077a0 100644
--- a/tools/perf/bench/futex-wake.c
+++ b/tools/perf/bench/futex-wake.c
@@ -191,6 +191,7 @@ int bench_futex_wake(int argc, const char **argv)
for (j = 0; j < bench_repeat && !done; j++) {
unsigned int nwoken = 0;
struct timeval start, end, runtime;
+ u64 runtime_us;
/* create, launch & block all threads */
block_threads(worker, cpu);
@@ -211,14 +212,15 @@ int bench_futex_wake(int argc, const char **argv)
params.nwakes, futex_flag);
gettimeofday(&end, NULL);
timersub(&end, &start, &runtime);
+ runtime_us = (u64)runtime.tv_sec * USEC_PER_SEC + runtime.tv_usec;
update_stats(&wakeup_stats, nwoken);
- update_stats(&waketime_stats, runtime.tv_usec);
+ update_stats(&waketime_stats, runtime_us);
if (!params.silent) {
printf("[Run %d]: Wokeup %d of %d threads in %.4f ms\n",
j + 1, nwoken, params.nthreads,
- runtime.tv_usec / (double)USEC_PER_MSEC);
+ runtime_us / (double)USEC_PER_MSEC);
}
for (i = 0; i < params.nthreads; i++) {
--
2.43.0