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Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
154 lines
2.9 KiB
C
154 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Test null syscall performance
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*
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* Copyright (C) 2009-2015 Anton Blanchard, IBM
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*/
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#define NR_LOOPS 10000000
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <time.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <signal.h>
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static volatile int soak_done;
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unsigned long long clock_frequency;
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unsigned long long timebase_frequency;
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double timebase_multiplier;
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static inline unsigned long mftb(void)
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{
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unsigned long low;
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asm volatile("mftb %0" : "=r" (low));
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return low;
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}
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static void sigalrm_handler(int unused)
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{
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soak_done = 1;
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}
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/*
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* Use a timer instead of busy looping on clock_gettime() so we don't
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* pollute profiles with glibc and VDSO hits.
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*/
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static void cpu_soak_usecs(unsigned long usecs)
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{
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struct itimerval val;
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memset(&val, 0, sizeof(val));
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val.it_value.tv_usec = usecs;
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signal(SIGALRM, sigalrm_handler);
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setitimer(ITIMER_REAL, &val, NULL);
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while (1) {
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if (soak_done)
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break;
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}
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signal(SIGALRM, SIG_DFL);
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}
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/*
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* This only works with recent kernels where cpufreq modifies
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* /proc/cpuinfo dynamically.
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*/
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static void get_proc_frequency(void)
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{
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FILE *f;
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char line[128];
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char *p, *end;
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unsigned long v;
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double d;
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char *override;
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/* Try to get out of low power/low frequency mode */
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cpu_soak_usecs(0.25 * 1000000);
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f = fopen("/proc/cpuinfo", "r");
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if (f == NULL)
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return;
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timebase_frequency = 0;
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while (fgets(line, sizeof(line), f) != NULL) {
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if (strncmp(line, "timebase", 8) == 0) {
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p = strchr(line, ':');
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if (p != NULL) {
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v = strtoull(p + 1, &end, 0);
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if (end != p + 1)
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timebase_frequency = v;
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}
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}
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if (((strncmp(line, "clock", 5) == 0) ||
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(strncmp(line, "cpu MHz", 7) == 0))) {
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p = strchr(line, ':');
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if (p != NULL) {
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d = strtod(p + 1, &end);
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if (end != p + 1) {
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/* Find fastest clock frequency */
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if ((d * 1000000ULL) > clock_frequency)
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clock_frequency = d * 1000000ULL;
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}
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}
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}
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}
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fclose(f);
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override = getenv("FREQUENCY");
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if (override)
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clock_frequency = strtoull(override, NULL, 10);
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if (timebase_frequency)
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timebase_multiplier = (double)clock_frequency
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/ timebase_frequency;
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else
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timebase_multiplier = 1;
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}
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static void do_null_syscall(unsigned long nr)
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{
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unsigned long i;
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for (i = 0; i < nr; i++)
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getppid();
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}
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#define TIME(A, STR) \
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int main(void)
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{
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unsigned long tb_start, tb_now;
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struct timespec tv_start, tv_now;
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unsigned long long elapsed_ns, elapsed_tb;
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get_proc_frequency();
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clock_gettime(CLOCK_MONOTONIC, &tv_start);
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tb_start = mftb();
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do_null_syscall(NR_LOOPS);
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clock_gettime(CLOCK_MONOTONIC, &tv_now);
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tb_now = mftb();
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elapsed_ns = (tv_now.tv_sec - tv_start.tv_sec) * 1000000000ULL +
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(tv_now.tv_nsec - tv_start.tv_nsec);
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elapsed_tb = tb_now - tb_start;
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printf("%10.2f ns %10.2f cycles\n", (float)elapsed_ns / NR_LOOPS,
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(float)elapsed_tb * timebase_multiplier / NR_LOOPS);
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return 0;
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}
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