1 /*
2 *
3 * Copyright 2015 gRPC authors.
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19 #ifndef _GNU_SOURCE
20 #define _GNU_SOURCE
21 #endif /* _GNU_SOURCE */
22
23 #include <grpc/support/port_platform.h>
24
25 #ifdef GPR_CPU_LINUX
26
27 #include <errno.h>
28 #include <sched.h>
29 #include <string.h>
30 #include <unistd.h>
31
32 #include <grpc/support/cpu.h>
33 #include <grpc/support/log.h>
34 #include <grpc/support/sync.h>
35
36 static int ncpus = 0;
37
init_num_cpus()38 static void init_num_cpus() {
39 #ifndef GPR_MUSL_LIBC_COMPAT
40 if (sched_getcpu() < 0) {
41 gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
42 ncpus = 1;
43 return;
44 }
45 #endif
46 /* This must be signed. sysconf returns -1 when the number cannot be
47 determined */
48 ncpus = static_cast<int>(sysconf(_SC_NPROCESSORS_CONF));
49 if (ncpus < 1) {
50 gpr_log(GPR_ERROR, "Cannot determine number of CPUs: assuming 1");
51 ncpus = 1;
52 }
53 }
54
gpr_cpu_num_cores(void)55 unsigned gpr_cpu_num_cores(void) {
56 static gpr_once once = GPR_ONCE_INIT;
57 gpr_once_init(&once, init_num_cpus);
58 return static_cast<unsigned>(ncpus);
59 }
60
gpr_cpu_current_cpu(void)61 unsigned gpr_cpu_current_cpu(void) {
62 #ifdef GPR_MUSL_LIBC_COMPAT
63 // sched_getcpu() is undefined on musl
64 return 0;
65 #else
66 if (gpr_cpu_num_cores() == 1) {
67 return 0;
68 }
69 int cpu = sched_getcpu();
70 if (cpu < 0) {
71 gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
72 return 0;
73 }
74 if (static_cast<unsigned>(cpu) >= gpr_cpu_num_cores()) {
75 gpr_log(GPR_DEBUG, "Cannot handle hot-plugged CPUs");
76 return 0;
77 }
78 return static_cast<unsigned>(cpu);
79 #endif
80 }
81
82 #endif /* GPR_CPU_LINUX */
83