我正尝试在使用openMP的单独CPU上运行两个进程。在这种情况下,每个CPU都有6个带超线程的核心(所以有12个硬件线程)。他们需要做一些同步,如果他们知道彼此的PID,看起来更容易一些。所以我正在从sigS
开始一个sigC
的过程,使用fork()
和execve()
为GOMP_CPU_AFFINITY
环境变量调用了一个不同的值。在fork()/execve()
电话后,sigS
具有正确的亲和力,但仍然打印sigC
无法在分叉进程中设置OpenMP线程关联
libgomp: no cpus left for affinity setting
和所有线程都在相同的核心。
的sigS
代码:
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <omp.h>
#include <sched.h>
int main(void)
{
omp_set_num_threads(12); //12 hardware threads per CPU
//this loop runs as expected
#pragma omp parallel for
for(int i = 0; i<12; i++) {
#pragma omp critical
{
printf("TEST PRE-FORK: I am thread %2d running on core %d\n",
omp_get_thread_num(), sched_getcpu());
}
}
pid_t childpid = fork();
if(childpid < 0) {
perror("Fork failed");
} else {
if(childpid == 0) { //<------ attempt to set affinity for child
//change the affinity for the other process so it runs
//on the other cpu
char ompEnv[] = "GOMP_CPU_AFFINITY=6-11 18-23";
char * const args[] = { "./sigC", (char*)0 };
char * const envArgs[] = { ompEnv, (char*)0 };
execve(args[0], args, envArgs);
perror("Returned from execve");
exit(1);
} else {
omp_set_num_threads(12);
printf("PARENT: my pid = %d\n", getpid());
printf("PARENT: child pid = %d\n", childpid);
sleep(5); //sleep for a bit so child process prints first
//This loop gives the same thread core/pairings as above
//this is expected
#pragma omp parallel for
for(int i = 0; i < 12; i++) {
#pragma omp critical
{
printf("PARENT: I'm thread %2d, on core %d.\n",
omp_get_thread_num(), sched_getcpu());
}
}
}
}
return 0;
}
的sigC
的代码只是有一个OMP平行for循环中,但为了完整性:
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <omp.h>
#include <sched.h>
int main(void)
{
omp_set_num_threads(12);
printf("CHILD: my pid = %d\n", getpid());
printf("CHILD: parent pid = %d\n", getppid());
//I expect this loop to have the core pairings as I specified in execve
//i.e thread 0 -> core 6, 1 -> 7, ... 6 -> 18, 7 -> 19 ... 11 -> 23
#pragma omp parallel for
for(int i = 0; i < 12; i++) {
#pragma omp critical
{
printf("CHILD: I'm thread %2d, on core %d.\n",
omp_get_thread_num(), sched_getcpu());
}
}
return 0;
}
输出:
$ env GOMP_CPU_AFFINITY="0-5 12-17" ./sigS
这部分如预期
TEST PRE-FORK: I'm thread 0, on core 0.
TEST PRE-FORK: I'm thread 11, on core 17.
TEST PRE-FORK: I'm thread 5, on core 5.
TEST PRE-FORK: I'm thread 6, on core 12.
TEST PRE-FORK: I'm thread 3, on core 3.
TEST PRE-FORK: I'm thread 1, on core 1.
TEST PRE-FORK: I'm thread 8, on core 14.
TEST PRE-FORK: I'm thread 10, on core 16.
TEST PRE-FORK: I'm thread 7, on core 13.
TEST PRE-FORK: I'm thread 2, on core 2.
TEST PRE-FORK: I'm thread 4, on core 4.
TEST PRE-FORK: I'm thread 9, on core 15.
PARENT: my pid = 11009
PARENT: child pid = 11021
这就是问题 - 在孩子的所有线程核心0
libgomp: no CPUs left for affinity setting
CHILD: my pid = 11021
CHILD: parent pid = 11009
CHILD: I'm thread 1, on core 0.
CHILD: I'm thread 0, on core 0.
CHILD: I'm thread 4, on core 0.
CHILD: I'm thread 5, on core 0.
CHILD: I'm thread 6, on core 0.
CHILD: I'm thread 7, on core 0.
CHILD: I'm thread 8, on core 0.
CHILD: I'm thread 9, on core 0.
CHILD: I'm thread 10, on core 0.
CHILD: I'm thread 11, on core 0.
CHILD: I'm thread 3, on core 0.
运行(我省略了父线程印刷,因为它是一样的预分叉)
任何关于如何解决这个问题或者如果这是正确的方法的想法?
请经常检查,如果你的代码示例编译在这里张贴他们的编译错误可能阻挠那些谁尝试之前解决你的问题。在这两个源代码中,'errno.h'中都有一个逗号而不是点,而'sigS'的源代码中有一个拼写错误('/'而不是'//')。 – 2013-03-06 21:27:48