mirror of
git://sourceware.org/git/glibc.git
synced 2024-11-27 03:41:23 +08:00
0997c3d0c8
Add a simple benchmark to measure the overhead of internal libc locks in the random() implementation on both single- and multi-threaded cases. This relies on the implementation of random using internal locks to access shared global data, and that the runtime uses multi-threaded locking once a thread has been created (even after it finishes). Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
107 lines
3.0 KiB
C
107 lines
3.0 KiB
C
/* 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"
|