[PATCH v4] benchtests: Add pthread mutex trylock throughput test (BZ #33704)

[Collin Funk]

"H.J. Lu" <hjl.tools@gmail.com> writes:

> On Sat, Dec 13, 2025 at 8:41 AM Sunil K Pandey <sunil.k.pandey@intel.com> wrote:
>>
>> This benchmark measures number of successful updates per second
>> under high cache contention.
>>
>> Tested on x86_64.
>> ---
>>  benchtests/Makefile                           |   2 +
>>  .../bench-pthread-mutex-trylock-throughput.c  | 177 ++++++++++++++++++
>>  2 files changed, 179 insertions(+)
>>  create mode 100644 benchtests/bench-pthread-mutex-trylock-throughput.c
>>
>> diff --git a/benchtests/Makefile b/benchtests/Makefile
>> index 2ecdde857e..c3368a7603 100644
>> --- a/benchtests/Makefile
>> +++ b/benchtests/Makefile
>> @@ -175,6 +175,7 @@ bench-pthread := \
>>    pthread-locks \
>>    pthread-mutex-lock \
>>    pthread-mutex-trylock \
>> +  pthread-mutex-trylock-throughput \
>>    pthread-spin-lock \
>>    pthread-spin-trylock \
>>    pthread_once \
>> @@ -188,6 +189,7 @@ bench-resolv := \
>>
>>  LDLIBS-bench-pthread-mutex-lock += -lm
>>  LDLIBS-bench-pthread-mutex-trylock += -lm
>> +LDLIBS-bench-pthread-mutex-trylock-throughput += -lm
>>  LDLIBS-bench-pthread-spin-lock += -lm
>>  LDLIBS-bench-pthread-spin-trylock += -lm
>>
>> diff --git a/benchtests/bench-pthread-mutex-trylock-throughput.c b/benchtests/bench-pthread-mutex-trylock-throughput.c
>> new file mode 100644
>> index 0000000000..72eb90e4d9
>> --- /dev/null
>> +++ b/benchtests/bench-pthread-mutex-trylock-throughput.c
>> @@ -0,0 +1,177 @@
>> +/* Measure pthread trylock throughput under high cache contention.
>> +   Copyright (C) 2025 Free Software Foundation, Inc.
>> +   This file is part of the GNU C Library.
>> +
>> +   The GNU C Library is free software; you can redistribute it and/or
>> +   modify it under the terms of the GNU Lesser General Public
>> +   License as published by the Free Software Foundation; either
>> +   version 2.1 of the License, or (at your option) any later version.
>> +
>> +   The GNU C Library is distributed in the hope that it will be useful,
>> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> +   Lesser General Public License for more details.
>> +
>> +   You should have received a copy of the GNU Lesser General Public
>> +   License along with the GNU C Library; if not, see
>> +   <https://www.gnu.org/licenses/>.  */
>> +
>> +#define TEST_MAIN
>> +#define TIMEOUT (20 * 60)
>> +#define TEST_NAME "pthread-mutex-trylock-throughput"
>> +
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +#include <math.h>
>> +#include <pthread.h>
>> +#include <sys/time.h>
>> +#include <sys/sysinfo.h>
>> +#include "bench-timing.h"
>> +#include "bench-util.h"
>> +#include "json-lib.h"
>> +
>> +#define ITERS 10000000
>> +#define RUN_COUNT 10
>> +
>> +pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
>> +
>> +/* Shared counter only incremented by successful threads.  */
>> +int counter = 0;
>> +
>> +static void *
>> +worker (void *v)
>> +{
>> +  for (int i = 0; i < ITERS; i++)
>> +    if (pthread_mutex_trylock(&mutex) == 0)
>> +      {
>> +       counter++;
>> +       pthread_mutex_unlock(&mutex);
>> +      }
>> +  return NULL;
>> +}
>> +
>> +static void
>> +do_bench_one (const char *name, int num_threads, int nprocs, json_ctx_t *js)
>> +{
>> +  struct timeval ts, te;
>> +  double tsd, ted, td, mean, stdev;
>> +  int i, j;
>> +  pthread_t *threads = malloc (num_threads * sizeof (pthread_t));
>> +
>> +  /* Array to hold throughput(#updates/second) result of each run.  We do
>> +     RUN_COUNT + 2 runs so that we can discard the highest and lowest as
>> +     outliers.  */
>> +  double throughput_count[RUN_COUNT + 2];
>> +
>> +  for (i = 0; i < RUN_COUNT + 2; i++)
>> +    {
>> +      /* Initialize counter before each run.  */
>> +      counter = 0;
>> +      gettimeofday (&ts, NULL);
>> +
>> +      for (j = 0; j < num_threads; j++)
>> +       pthread_create (&threads[j], NULL, worker, NULL);
>> +
>> +      for (j = 0; j < num_threads; j++)
>> +       pthread_join (threads[j], NULL);
>> +      gettimeofday (&te, NULL);
>> +      tsd = ts.tv_sec + ts.tv_usec / 1000000.0;
>> +      ted = te.tv_sec + te.tv_usec / 1000000.0;
>> +      td = ted - tsd;
>> +
>> +      /* Number of successful updates per second.  */
>> +      throughput_count[i] = counter / td;
>> +    }
>> +
>> +  free (threads);
>> +
>> +  /* Sort the results so we can discard the largest and smallest
>> +     throughput as outliers.  */
>> +  for (i = 0; i < RUN_COUNT + 1; i++)
>> +    for (j = i + 1; j < RUN_COUNT + 2; j++)
>> +      if (throughput_count[i] > throughput_count[j])
>> +       {
>> +         double temp = throughput_count[i];
>> +         throughput_count[i] = throughput_count[j];
>> +         throughput_count[j] = temp;
>> +       }
>> +
>> +  /* Calculate mean and standard deviation.  */
>> +  mean = 0;
>> +  for (i = 1; i < RUN_COUNT + 1; i++)
>> +    mean += throughput_count[i];
>> +  mean /= RUN_COUNT;
>> +
>> +  stdev = 0.0;
>> +  for (i = 1; i < RUN_COUNT + 1; i++)
>> +    {
>> +      double s = throughput_count[i] - mean;
>> +      stdev += s * s;
>> +    }
>> +  stdev = sqrt (stdev / (RUN_COUNT - 1));
>> +
>> +  char buf[256];
>> +  snprintf (buf, sizeof buf, "%s,threads=%d,HW threads=%d", name, num_threads,
>> +           nprocs);
>> +
>> +  json_attr_object_begin (js, buf);
>> +
>> +  json_attr_uint (js, "mean", mean);
>> +  json_attr_uint (js, "stdev", stdev);
>> +  json_attr_uint (js, "min-outlier", throughput_count[0]);
>> +  json_attr_uint (js, "min", throughput_count[1]);
>> +  json_attr_uint (js, "max", throughput_count[RUN_COUNT]);
>> +  json_attr_uint (js, "max-outlier", throughput_count[RUN_COUNT + 1]);
>> +
>> +  json_attr_object_end (js);
>> +}
>> +
>> +int
>> +do_bench (void)
>> +{
>> +  int rv = 0;
>> +  json_ctx_t json_ctx;
>> +  int th_num, th_conf, nprocs;
>> +  char name[128];
>> +
>> +  json_init (&json_ctx, 2, stdout);
>> +  json_attr_object_begin (&json_ctx, TEST_NAME);
>> +
>> +  /* The thread config begins from 2, and increases by 2x until nprocs.
>> +     We also want to test nprocs and over-saturation case 2*nprocs and
>> +     4*nprocs.  */
>> +  nprocs = get_nprocs ();
>> +
>> +  /* Allocate [nprocs + 2] thread config array.  */
>> +  int *threads = malloc ((nprocs + 2) * sizeof (int));
>> +
>> +  th_num = 2;
>> +  for (th_conf = 0; th_num < nprocs; th_conf++)
>> +    {
>> +      threads[th_conf] = th_num;
>> +      th_num <<= 1;
>> +    }
>> +  threads[th_conf++] = nprocs;
>> +  threads[th_conf++] = nprocs * 2;
>> +  threads[th_conf++] = nprocs * 4;
>> +
>> +  snprintf (name, sizeof name, "type=throughput(#updates/second)");
>> +
>> +  for (int i = 0; i < th_conf; i++)
>> +    {
>> +      th_num = threads[i];
>> +      do_bench_one (name, th_num, nprocs, &json_ctx);
>> +    }
>> +
>> +  free (threads);
>> +
>> +  json_attr_object_end (&json_ctx);
>> +
>> +  return rv;
>> +}
>> +
>> +#define TEST_FUNCTION do_bench ()
>> +
>> +#include "../test-skeleton.c"
>> --
>> 2.51.0
>>
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Shouldn't new tests be using support/test-driver.c instead of the old
test-skeleton.c?

Sorry I didn't notice before your review.

Collin