Question

我如何知道在C程序中，我的代码运行在哪个物理处理器和核心上？我正在使用Linux和gcc 4.4.3。

Answer 1

sched_getcpu()

调用返回虚拟CPU编号。虚拟CPU到实际CPU信息的映射在/ proc / cpuinfo。

如果您的系统支持VDSO，则sched_getcpu()相对较快。

也可以使用CPUID指令获取CPU编号，但速度比sched_getcpu()慢。

Answer 2

请参阅http://en.wikipedia.org/wiki/CPUID#Accessing_the_id_from_other_languages

你想要的是APIC ID ...基本上：

    cpuid
    shr     ebx, 24

Answer 3

您可以使用GCC获得进程与处理器的亲和力。 CPU affinity API可能会帮助您。您是否尝试使用此信息来确保您的流程不会中断或执行如此高优先级的任务？

Answer 4

您可以检查/ proc // stat文件系统，根据http://www.kernel.org/doc/Documentation/filesystems/proc.txt，您应该只检查task_cpu标志。

作为没有正确类型和错误检查的示例：

struct pstat
{
  int  pid;       //process id
  char tcomm[256];//filename of the executable
  char state[2];  //state (R is running, S is sleeping, D is sleeping in an
                  //uninterruptible wait, Z is zombie, T is traced or stopped)
  int ppid;//          process id of the parent process
  int pgrp;//          pgrp of the process
  int sid;//           session id
  int tty_nr;//        tty the process uses
  int tty_pgrp;//      pgrp of the tty
  int flags;//         task flags
  int min_flt;//       number of minor faults
  int cmin_flt;//      number of minor faults with child's
  int maj_flt;//       number of major faults
  int cmaj_flt;//      number of major faults with child's
  int utime;//         user mode jiffies
  int stime;//         kernel mode jiffies
  int cutime;//        user mode jiffies with child's
  int cstime;//        kernel mode jiffies with child's
  int priority;//      priority level
  int nice;//          nice level
  int num_threads;//   number of threads
  int it_real_value;//  (obsolete, always 0)
  int start_time;//    time the process started after system boot
  int vsize;//         virtual memory size
  int rss;//           resident set memory size
  int rsslim;//        current limit in bytes on the rss
  int start_code;//    address above which program text can run
  int end_code;//      address below which program text can run
  int start_stack;//   address of the start of the stack
  int esp;//           current value of ESP
  int eip;//           current value of EIP
  int pending;//       bitmap of pending signals
  int blocked;//       bitmap of blocked signals
  int sigign;//        bitmap of ignored signals
  int sigcatch;//      bitmap of catched signals
  int wchan;//         address where process went to sleep
  int i0;//             (place holder)
  int i1;//             (place holder)
  int exit_signal;//   signal to send to parent thread on exit
  int task_cpu;//      which CPU the task is scheduled on
  int rt_priority;//   realtime priority
  int policy;//        scheduling policy (man sched_setscheduler)
  int blkio_ticks;//   time spent waiting for block IO
  int gtime;//         guest time of the task in jiffies
  int cgtime;//        guest time of the task children in jiffies
} p ;

int main()
{
    char name[256];
    char state[8];
    FILE* f = fopen("/proc/self/stat", "r");

    fscanf(f,  "%d%s%s%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d",
           &p.pid, &p.tcomm, &p.state, &p.ppid, &p.pgrp, &p.sid, &p.tty_nr, &p.tty_pgrp, &p.flags,
           &p.min_flt, &p.cmin_flt, &p.maj_flt, &p.cmaj_flt, &p.utime, &p.stime,  &p.cutime, &p.cstime,
           &p.priority, &p.nice, &p.num_threads, &p.it_real_value, &p.start_time,  &p.vsize, &p.rss,
           &p.rsslim, &p.start_code, &p.end_code, &p.start_stack, &p.esp, &p.eip,  &p.pending, &p.blocked,
           &p.sigign, &p.sigcatch, &p.wchan, &p.i0, &p.i1, &p.exit_signal,  &p.task_cpu, &p.rt_priority, &p.policy,
           &p.blkio_ticks, &p.gtime, &p.cgtime);

     printf("CPU %d\n", p.task_cpu);
 return 0;  
 }

Answer 5

总的来说，很难以有意义的方式找到它。您的线程通常会在其生命周期中运行在许多不同的处理器上您可以调用一个函数来询问您所在的处理器，并在函数执行时获取上下文切换。该函数应该返回什么？

如何知道我的代码运行在哪个物理处理器和哪个物理核心上

5 个答案: