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/* Benchmark internal libc locking functions used in random.
Copyright (C) 2022-2024 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 TEST_NAME "random-lock"
#define TEST_FUNCTION test_main
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include "bench-timing.h"
#include "json-lib.h"
/* Modern cores run 20M iterations in about 1 second. */
#define NUM_ITERS 50000000
/* Measure the overhead of __libc_lock_lock and __libc_lock_unlock by
calling random (). */
static void
bench_random_lock (json_ctx_t *json_ctx, size_t iters)
{
timing_t start, stop, total;
srandom (0);
/* Warmup to reduce variations due to frequency scaling. */
for (int i = 0; i < iters / 4; i++)
(void) random ();
TIMING_NOW (start);
for (int i = 0; i < iters; i++)
(void) random ();
TIMING_NOW (stop);
TIMING_DIFF (total, start, stop);
json_element_double (json_ctx, (double) total / (double) iters);
}
static void *
thread_start (void *p)
{
return p;
}
int
test_main (void)
{
json_ctx_t json_ctx;
json_init (&json_ctx, 0, stdout);
json_document_begin (&json_ctx);
json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
json_attr_object_begin (&json_ctx, "functions");
json_attr_object_begin (&json_ctx, "random");
json_attr_string (&json_ctx, "bench-variant", "single-threaded");
json_array_begin (&json_ctx, "results");
/* Run benchmark single threaded. */
bench_random_lock (&json_ctx, NUM_ITERS);
json_array_end (&json_ctx);
json_attr_object_end (&json_ctx);
json_attr_object_begin (&json_ctx, "random");
json_attr_string (&json_ctx, "bench-variant", "multi-threaded");
json_array_begin (&json_ctx, "results");
/* Start a short thread to force SINGLE_THREAD_P == false. This relies on
the runtime disabling single-threaded optimizations when multiple
threads are used, even after they finish. */
pthread_t t;
pthread_create (&t, NULL, thread_start, NULL);
pthread_join (t, NULL);
/* Repeat benchmark with single-threaded optimizations disabled. */
bench_random_lock (&json_ctx, NUM_ITERS);
json_array_end (&json_ctx);
json_attr_object_end (&json_ctx);
json_attr_object_end (&json_ctx);
json_document_end (&json_ctx);
return 0;
}
#include "support/test-driver.c"
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