1 /* Copyright (c) 2003-2004, Roger Dingledine
2 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
3 * Copyright (c) 2007-2021, The Tor Project, Inc. */
4 /* See LICENSE for licensing information */
5
6 /**
7 * \file numcpus.c
8 * \brief Compute the number of CPUs configured on this system.
9 **/
10
11 #include "orconfig.h"
12 #include "lib/thread/numcpus.h"
13 #include "lib/log/log.h"
14 #include "lib/log/util_bug.h"
15
16 #ifdef HAVE_UNISTD_H
17 #include <unistd.h>
18 #endif
19 #ifdef _WIN32
20 #include <windows.h>
21 #endif
22
23 #include <stdlib.h>
24
25 /** Implementation logic for compute_num_cpus(). */
26 static int
compute_num_cpus_impl(void)27 compute_num_cpus_impl(void)
28 {
29 #ifdef _WIN32
30 SYSTEM_INFO info;
31 memset(&info, 0, sizeof(info));
32 GetSystemInfo(&info);
33 if (info.dwNumberOfProcessors >= 1 && info.dwNumberOfProcessors < INT_MAX)
34 return (int)info.dwNumberOfProcessors;
35 else
36 return -1;
37 #elif defined(HAVE_SYSCONF)
38 #ifdef _SC_NPROCESSORS_CONF
39 long cpus_conf = sysconf(_SC_NPROCESSORS_CONF);
40 #else
41 long cpus_conf = -1;
42 #endif
43 #ifdef _SC_NPROCESSORS_ONLN
44 long cpus_onln = sysconf(_SC_NPROCESSORS_ONLN);
45 #else
46 long cpus_onln = -1;
47 #endif
48 long cpus = -1;
49
50 if (cpus_conf > 0 && cpus_onln < 0) {
51 cpus = cpus_conf;
52 } else if (cpus_onln > 0 && cpus_conf < 0) {
53 cpus = cpus_onln;
54 } else if (cpus_onln > 0 && cpus_conf > 0) {
55 if (cpus_onln < cpus_conf) {
56 log_notice(LD_GENERAL, "I think we have %ld CPUS, but only %ld of them "
57 "are available. Telling Tor to only use %ld. You can over"
58 "ride this with the NumCPUs option",
59 cpus_conf, cpus_onln, cpus_onln);
60 }
61 cpus = cpus_onln;
62 }
63
64 if (cpus >= 1 && cpus < INT_MAX)
65 return (int)cpus;
66 else
67 return -1;
68 #else
69 return -1;
70 #endif /* defined(_WIN32) || ... */
71 }
72
73 #define MAX_DETECTABLE_CPUS 16
74
75 /** Return how many CPUs we are running with. We assume that nobody is
76 * using hot-swappable CPUs, so we don't recompute this after the first
77 * time. Return -1 if we don't know how to tell the number of CPUs on this
78 * system.
79 */
80 int
compute_num_cpus(void)81 compute_num_cpus(void)
82 {
83 static int num_cpus = -2;
84 if (num_cpus == -2) {
85 num_cpus = compute_num_cpus_impl();
86 tor_assert(num_cpus != -2);
87 if (num_cpus > MAX_DETECTABLE_CPUS) {
88 /* LCOV_EXCL_START */
89 log_notice(LD_GENERAL, "Wow! I detected that you have %d CPUs. I "
90 "will not autodetect any more than %d, though. If you "
91 "want to configure more, set NumCPUs in your torrc",
92 num_cpus, MAX_DETECTABLE_CPUS);
93 num_cpus = MAX_DETECTABLE_CPUS;
94 /* LCOV_EXCL_STOP */
95 }
96 }
97 return num_cpus;
98 }
99