Attachment 301635 Details for Bug 433659 – possibly fixed get_clock.c

possibly fixed get_clock.c

get_clock.c (text/plain), 4.93 KB, created by Doug Ledford on 2008-04-08 14:22:32 UTC

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Creator: Doug Ledford

Created: 2008-04-08 14:22:32 UTC

Size: 4.93 KB

patch

obsolete

>/*
> * Copyright (c) 2005 Mellanox Technologies Ltd.  All rights reserved.
> *
> * This software is available to you under a choice of one of two
> * licenses.  You may choose to be licensed under the terms of the GNU
> * General Public License (GPL) Version 2, available from the file
> * COPYING in the main directory of this source tree, or the
> * OpenIB.org BSD license below:
> *
> *     Redistribution and use in source and binary forms, with or
> *     without modification, are permitted provided that the following
> *     conditions are met:
> *
> *      - Redistributions of source code must retain the above
> *        copyright notice, this list of conditions and the following
> *        disclaimer.
> *
> *      - Redistributions in binary form must reproduce the above
> *        copyright notice, this list of conditions and the following
> *        disclaimer in the documentation and/or other materials
> *        provided with the distribution.
> *
> * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
> * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
> * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
> * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
> * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
> * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
> * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
> * SOFTWARE.
> *
> * $Id$
> *
> * Author: Michael S. Tsirkin <mst@mellanox.co.il>
> */
>
>/* #define DEBUG 1 */
>/* #define DEBUG_DATA 1 */
>/* #define GET_CPU_MHZ_FROM_PROC 1 */
>
>/* For gettimeofday */
>#define _BSD_SOURCE
>#include <sys/time.h>
>
>#include <unistd.h>
>#include <stdio.h>
>#include "get_clock.h"
>
>#ifndef DEBUG
>#define DEBUG 0
>#endif
>#ifndef DEBUG_DATA
>#define DEBUG_DATA 0
>#endif
>
>#define MEASUREMENTS 200
>#define USECSTEP 10
>#define USECSTART 100
>
>/*
> Use linear regression to calculate cycles per microsecond.
> http://en.wikipedia.org/wiki/Linear_regression#Parameter_estimation
>*/
>static double sample_get_cpu_mhz(void)
>{
>	struct timeval tv1, tv2;
>	cycles_t start;
>	double sx = 0, sy = 0, sxx = 0, syy = 0, sxy = 0;
>	double tx, ty;
>	int i;
>
>	/* Regression: y = a + b x */
>	long x[MEASUREMENTS];
>	cycles_t y[MEASUREMENTS];
>	double a; /* system call overhead in cycles */
>	double b; /* cycles per microsecond */
>	double r_2;
>
>	for (i = 0; i < MEASUREMENTS; ++i) {
>		start = get_cycles();
>
>		if (gettimeofday(&tv1, NULL)) {
>			fprintf(stderr, "gettimeofday failed.\n");
>			return 0;
>		}
>
>		do {
>			if (gettimeofday(&tv2, NULL)) {
>				fprintf(stderr, "gettimeofday failed.\n");
>				return 0;
>			}
>		} while ((tv2.tv_sec - tv1.tv_sec) * 1000000 +
>			(tv2.tv_usec - tv1.tv_usec) < USECSTART + i * USECSTEP);
>
>		x[i] = (tv2.tv_sec - tv1.tv_sec) * 1000000 +
>			tv2.tv_usec - tv1.tv_usec;
>		y[i] = get_cycles() - start;
>		if (DEBUG_DATA)
>			fprintf(stderr, "x=%ld y=%Ld\n", x[i], (long long)y[i]);
>	}
>
>	for (i = 0; i < MEASUREMENTS; ++i) {
>		tx = x[i];
>		ty = y[i];
>		sx += tx;
>		sy += ty;
>		sxx += tx * tx;
>		syy += ty * ty;
>		sxy += tx * ty;
>	}
>	
>	b = (MEASUREMENTS * sxy - sx * sy) / (MEASUREMENTS * sxx - sx * sx);
>	a = (sy - b * sx) / MEASUREMENTS;
>
>	if (DEBUG)
>		fprintf(stderr, "a = %g\n", a);
>	if (DEBUG)
>		fprintf(stderr, "b = %g\n", b);
>	if (DEBUG)
>		fprintf(stderr, "a / b = %g\n", a / b);
>	r_2 = (MEASUREMENTS * sxy - sx * sy) * (MEASUREMENTS * sxy - sx * sy) /
>		(MEASUREMENTS * sxx - sx * sx) /
>		(MEASUREMENTS * syy - sy * sy);
>
>	if (DEBUG)
>		fprintf(stderr, "r^2 = %g\n", r_2);
>	if (r_2 < 0.9) {
>		fprintf(stderr,"Correlation coefficient r^2: %g < 0.9\n", r_2);
>		return 0;
>	}
>
>	return b;
>}
>
>static double proc_get_cpu_mhz(void)
>{
>	FILE* f;
>	char buf[256];
>	double mhz = 0.0;
>
>	f = fopen("/proc/cpuinfo","r");
>	if (!f)
>		return 0.0;
>	while(fgets(buf, sizeof(buf), f)) {
>		double m;
>		int rc;
>		rc = sscanf(buf, "cpu MHz : %lf", &m);
>		if (rc != 1) {	/* PPC has a different format */
>			rc = sscanf(buf, "clock : %lf", &m);
>			if (rc != 1)
>				continue;
>		}
>		if (mhz == 0.0) {
>			mhz = m;
>			continue;
>		}
>		if (mhz != m) {
>			fprintf(stderr, "Conflicting CPU frequency values"
>				" detected: %lf != %lf\n", mhz, m);
>			return 0.0;
>		}
>	}
>	fclose(f);
>	return mhz;
>}
>
>
>double get_cpu_mhz(void)
>{
>#if defined(__ia64)
>	double i;
>#endif
>	double sample, proc, delta;
>	sample = sample_get_cpu_mhz();
>	proc = proc_get_cpu_mhz();
>
>	if (!proc || !sample)
>		return 0;
>#if defined(__ia64)
>	/*
>	 * We use the itc clock on ia64 to get cpu cycles, but the cpu
>	 * clock may be a multiple of the itc clock.  Try to pull out
>	 * the multiple and then check for variance between proc and sample.
>	 */
>	for (i=1; i <= 10; i += .5) {
>		delta = proc > (sample * i) ? proc - (sample * i) :
>			(sample * i) - proc;
>		if (delta / proc < .05)
>			break;
>	}
>	if (i != 10.5)
>		sample *= i;
>#endif
>	delta = proc > sample ? proc - sample : sample - proc;
>	if (delta / proc > 0.01) {
>			fprintf(stderr, "Warning: measured timestamp frequency "
>					"%g differs from nominal %g MHz\n",
>					sample, proc);
>			return sample;
>	}
>	return proc;
>}

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Attachments on bug 433659: 301633 | 301634 | 301635