如何使用 C 获取 Linux 中的 CPU 数量？
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How to get the number of CPUs in Linux using C?
提问by Trevi?o
Is there an API to get the number of CPUs available in Linux? I mean, without using /proc/cpuinfo or any other sys-node file...
是否有用于获取 Linux 中可用 CPU 数量的 API？我的意思是，不使用 /proc/cpuinfo 或任何其他 sys-node 文件...
I've found this implementation using sched.h:
我使用 sched.h 找到了这个实现：
int GetCPUCount()
{
cpu_set_t cs;
CPU_ZERO(&cs);
sched_getaffinity(0, sizeof(cs), &cs);
int count = 0;
for (int i = 0; i < 8; i++)
{
if (CPU_ISSET(i, &cs))
count++;
}
return count;
}
But, isn't there anything more higher level using common libraries?
但是，使用公共库没有更高级别的东西吗？
采纳答案by Владимир Николайчук
#include <stdio.h>
#include <sys/sysinfo.h>
int main(int argc, char *argv[])
{
printf("This system has %d processors configured and "
"%d processors available.\n",
get_nprocs_conf(), get_nprocs());
return 0;
}
回答by chrisaycock
#include <unistd.h>
long number_of_processors = sysconf(_SC_NPROCESSORS_ONLN);
回答by R.. GitHub STOP HELPING ICE
Using /proc/cpuinfois the cleanest and most portable solution. In case the open fails, you could simply assume 1 cpu or 2 cpus. Code that depends on knowing the number of cpus for a purpose other than micro-optimizing (e.g. choosing the ideal number of threads to run) is almost surely doing something dumb.
使用/proc/cpuinfo是最干净、最便携的解决方案。如果打开失败，您可以简单地假设 1 个 cpu 或 2 个 cpu。出于微优化以外的目的（例如选择要运行的理想线程数）而依赖于了解 CPU 数量的代码几乎肯定会做一些愚蠢的事情。
The _SC_NPROCESSORS_ONLNsolution depends on a non-standard (glibc-specific) sysconfextension, which is a much bigger dependency than /proc(all Linux systems have /proc, but some have non-glibc libcs or older versions of glibc that lack _SC_NPROCESSORS_ONLN).
该_SC_NPROCESSORS_ONLN解决方案依赖于非标准（glibc 特定）sysconf扩展，它比/proc（所有 Linux 系统都有/proc，但有些具有非 glibc libcs 或缺少 的旧版 glibc _SC_NPROCESSORS_ONLN）具有更大的依赖性。
回答by Vikram.exe
This code (drawn from here) should work on both windows and *NIX platforms.
这段代码（从这里提取）应该适用于 windows 和 *NIX 平台。
#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#else
#include <unistd.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
int main() {
long nprocs = -1;
long nprocs_max = -1;
#ifdef _WIN32
#ifndef _SC_NPROCESSORS_ONLN
SYSTEM_INFO info;
GetSystemInfo(&info);
#define sysconf(a) info.dwNumberOfProcessors
#define _SC_NPROCESSORS_ONLN
#endif
#endif
#ifdef _SC_NPROCESSORS_ONLN
nprocs = sysconf(_SC_NPROCESSORS_ONLN);
if (nprocs < 1)
{
fprintf(stderr, "Could not determine number of CPUs online:\n%s\n",
strerror (errno));
exit (EXIT_FAILURE);
}
nprocs_max = sysconf(_SC_NPROCESSORS_CONF);
if (nprocs_max < 1)
{
fprintf(stderr, "Could not determine number of CPUs configured:\n%s\n",
strerror (errno));
exit (EXIT_FAILURE);
}
printf ("%ld of %ld processors online\n",nprocs, nprocs_max);
exit (EXIT_SUCCESS);
#else
fprintf(stderr, "Could not determine number of CPUs");
exit (EXIT_FAILURE);
#endif
}
回答by RCL
sched_affinity()version you mention in the beginning is still better than /proc/cpuinfoand/or _SC_NPROCESSORS_ONLNsince it only counts CPUs available for a given process (some may be disabled by sched_setaffinity()invoked by an outside process). The only change would be using CPU_COUNT()instead of doing CPU_ISSETin a loop.
sched_affinity()您在开头提到的版本仍然比/proc/cpuinfo和/或_SC_NPROCESSORS_ONLN因为它只计算给定进程可用的 CPU 数（有些可能被sched_setaffinity()外部进程调用而被禁用）更好。唯一的变化是使用CPU_COUNT()而不是CPU_ISSET在循环中进行。
回答by Sunil Bojanapally
Another method scanning cpu* directories under sys file system:
另一种扫描sys文件系统下cpu*目录的方法：
#include<stdio.h>
#include <dirent.h>
#include <errno.h>
#define LINUX_SYS_CPU_DIRECTORY "/sys/devices/system/cpu"
int main() {
int cpu_count = 0;
DIR *sys_cpu_dir = opendir(LINUX_SYS_CPU_DIRECTORY);
if (sys_cpu_dir == NULL) {
int err = errno;
printf("Cannot open %s directory, error (%d).\n", LINUX_SYS_CPU_DIRECTORY, strerror(err));
return -1;
}
const struct dirent *cpu_dir;
while((cpu_dir = readdir(sys_cpu_dir)) != NULL) {
if (fnmatch("cpu[0-9]*", cpu_dir->d_name, 0) != 0)
{
/* Skip the file which does not represent a CPU */
continue;
}
cpu_count++;
}
printf("CPU count: %d\n", cpu_count);
return 0;
}
回答by Zibri
Personally for recent intel cpus I use this:
我个人对于最近的英特尔 CPU 使用这个：
int main()
{
unsigned int eax=11,ebx=0,ecx=1,edx=0;
asm volatile("cpuid"
: "=a" (eax),
"=b" (ebx),
"=c" (ecx),
"=d" (edx)
: "0" (eax), "2" (ecx)
: );
printf("Cores: %d\nThreads: %d\nActual thread: %d\n",eax,ebx,edx);
}
Output:
输出：
Cores: 4
Threads: 8
Actual thread: 1
Or, more concisely:
或者，更简洁地说：
#include <stdio.h>
int main()
{
unsigned int ncores=0,nthreads=0,ht=0;
asm volatile("cpuid": "=a" (ncores), "=b" (nthreads) : "a" (0xb), "c" (0x1) : );
ht=(ncores!=nthreads);
printf("Cores: %d\nThreads: %d\nHyperThreading: %s\n",ncores,nthreads,ht?"Yes":"No");
return 0;
}
Output:
输出：
Cores: 4
Threads: 8
HyperThreading: Yes
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