1 /*
2 * cycles.c - measures CPU cycles using architecture specific extensions.
3 *
4 * Currently just for the pentium using the RDTSC instruction
5 *
6 * Copyright (c) 1998 Phil Maker <pjm@gnu.org>
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 * $Id: cycles.c,v 1.1.1.1 1999/09/12 03:26:50 pjm Exp $
31 */
32
33 #include <nana-config.h>
34
35 #if HAVE_CYCLES /* only compile this file if we can measure CPU cycles */
36
37 #include <now.h>
38 #include <cycles.h>
39
40 /*
41 * measure - does a single measurement using a spin loop running for
42 * duration. Sets min/max appropriately (note: min is the smallest
43 * number of the cps which is the LONGEST time!)
44 *
45 * Assumptions:
46 *
47 * 1. We can be preempted by another process at any time;
48 * hence the min..max return values.
49 * 2. We use doubles for some of the calculations and this
50 * should be allright since the number of cycles occurring
51 * during a single measurement should be representable in
52 * in a double (I hope).
53 */
54
measure(double duration,CYCLES * min,CYCLES * max)55 static void measure(double duration, CYCLES *min, CYCLES *max) {
56 double start_min, start_max, end_min, end_max;
57 CYCLES start, end;
58
59 start_min = now();
60 start = cycles();
61 start_max = now();
62
63 do {
64 end_min = now();
65 } while((end_min - start_min) < duration);
66
67 end = cycles();
68 end_max = now();
69
70 *max = (CYCLES) (((double)(end - start))/(end_min - start_max));
71 *min = (CYCLES) (((double)(end - start))/(end_max - start_min));
72 }
73
74 static CYCLES min_cps, max_cps;
75
76 /*
77 * cycles_per_second - performs n measurements of duration d and returns
78 * the maximum value which should be fairly close to the correct
79 * value (and pigs fly). The values min_cps and max_cps are reset
80 * upon every call to this routine.
81 */
82
cycles_per_second(double d,int n)83 CYCLES cycles_per_second(double d, int n) {
84 int i;
85 CYCLES min, max;
86
87 measure(d, &min_cps, &max_cps);
88 for(i = 1; i < n; i++) {
89 measure(d, &min, &max);
90 if(min < min_cps) {
91 min_cps = min;
92 }
93 if(max > max_cps) {
94 max_cps = max;
95 }
96 }
97 return max_cps;
98 }
99
cycles_per_second_min()100 CYCLES cycles_per_second_min() {
101 return min_cps;
102 }
103
cycles_per_second_max()104 CYCLES cycles_per_second_max() {
105 return max_cps;
106 }
107
cycles_diff(CYCLES start,CYCLES stop)108 double cycles_diff(CYCLES start, CYCLES stop) {
109 return ((double)(stop - start))/((double) max_cps);
110
111 }
112
113 #endif /* HAVE_CYCLES */
114
115