affinity.h revision e2d32e4c57b4a83841288c4010a653885fdb9606 
1/*
2 *
3 *   Copyright (c) Novell Inc. 2011
4 *
5 *   This program is free software;  you can redistribute it and/or modify
6 *   it under the terms in version 2 of the GNU General Public License as
7 *   published by the Free Software Foundation.
8 *
9 *   This program is distributed in the hope that it will be useful,
10 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
11 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
12 *   the GNU General Public License for more details.
13 *
14 *   You should have received a copy of the GNU General Public License
15 *   along with this program;  if not, write to the Free Software
16 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 *
18 *   Author:  Peter W. Morreale <pmorreale AT novell DOT com>
19 *   Date:    11/08/2011
20 */
21
22/*
23 * Must be ported to OS's other than Linux
24 */
25
26#ifdef __linux__
27# define _GNU_SOURCE
28# define AFFINITY_NEEDS_GNU_SOURCE 1
29# include <sched.h>
30# include <stdio.h>
31
32static int set_affinity(int cpu)
33{
34	cpu_set_t mask;
35
36	CPU_ZERO(&mask);
37	CPU_SET(cpu, &mask);
38
39	return (sched_setaffinity(0, sizeof(cpu_set_t), &mask));
40}
41
42static int get_online_cpu_from_sysfs(void)
43{
44	FILE *f;
45	int cpu = -1;
46
47	f = fopen("/sys/devices/system/cpu/online", "r");
48	if (!f)
49		return -1;
50	fscanf(f, "%d", &cpu);
51	fclose(f);
52
53	return cpu;
54}
55
56static int get_online_cpu_from_cpuinfo(void)
57{
58	FILE *f;
59	int cpu = -1;
60	char line[4096];
61
62	f = fopen("/proc/cpuinfo", "r");
63	if (!f)
64		return -1;
65
66	while (!feof(f)) {
67		if (!fgets(line, sizeof(line), f))
68			return -1;
69		/*
70		 * cpuinfo output is not consistent across all archictures,
71		 * it can be "processor        : N", but for example on s390
72		 * it's: "processor N: ...", so ignore any non-number
73		 * after "processor"
74		 */
75		if (sscanf(line, "processor%*[^0123456789]%d", &cpu) == 1)
76			break;
77	}
78	fclose(f);
79
80	return cpu;
81}
82
83static int set_affinity_single(void)
84{
85	int cpu;
86
87	cpu = get_online_cpu_from_sysfs();
88	if (cpu >= 0)
89		goto set_affinity;
90
91	cpu = get_online_cpu_from_cpuinfo();
92	if (cpu >= 0)
93		goto set_affinity;
94
95	fprintf(stderr, "WARNING: Failed to detect online cpu, using cpu=0\n");
96	cpu = 0;
97set_affinity:
98	return set_affinity(cpu);
99}
100
101#else
102static int set_affinity_single(void)
103{
104	errno = ENOSYS;
105	return -1;
106}
107#endif
108