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linux - 如何设置 OpenMP 以使用整个超线程进行并行处理？

问题描述

请帮助我，我想在我的程序中使用 OpenMP 进行所有线程的并行处理。我设置它同样如下：

    #pragma omp parallel
    {
       omp_set_num_threads(272);
       region my_routine processing;
    }

当我执行它时，我使用编译器“top”来检查 CPU 使用的性能，只是有时它存档 6800%（几乎低于 5500%）——它不稳定。我希望它在我的程序执行期间保持稳定（总是存档 6800%）。

使用 OpenMP 哪里出了问题，或者我们有任何其他方法可以使用整个线程？

非常感谢。

这是我的平台：

Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                272
On-line CPU(s) list:   0-271
Thread(s) per core:    4
Core(s) per socket:    68
Socket(s):             1
NUMA node(s):          2
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 87
Model name:            Intel(R) Xeon Phi(TM) CPU 7250 @ 1.40GHz
Stepping:              1
CPU MHz:               1392.507
BogoMIPS:              2799.81
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              1024K
NUMA node0 CPU(s):     0-271
NUMA node1 CPU(s):

标签： linuxparallel-processingopenmp

解决方案

第 0 步：安全第一：
与您的集群提供商 HPC 支持团队核实，他们是否认为在其拥有/运营的集群设备上设置如此高级别的工作负载无害。

第 1 步：设置“冒烟”飞行测试
准备lstopo命令（apt-get或要求管理员修复此问题，如有必要）并将系统的 NUMA 拓扑图创建为 pdf 文件并在此处发布
准备htop命令（apt-get或要求如有必要，请您的管理员解决此问题），将 设置
配置为显示到左侧面板， 设置为显示到左侧面板，设置为至少显示列字段F2
METERSCPUs (1&2/4): first half in 2 shorter columnsMONITOR
METERSCPUs (3&4/4): second half in 2 shorter columnsMONITOR
COLUMNS{ PPID, PID, TGID, CPU, CPU%, STATUS, command }

第 2 步：运行htop-monitor，运行编译后的 OpenMP 代码

期望在终端 CLI 上出现高于此值的内容，但htop-monitor 将比任何单个数字更好地显示 NUMA-CPU-workloads 的实时场景景观：

Real time: 23.027 s
User time: 45.337 s
Sys. time: 0.047 s
Exit code: 0

stdout将阅读此内容：

WARMUP: OpenMP thread[  0] instantiated as thread[  0]
WARMUP: OpenMP thread[  3] instantiated as thread[  3]
...
WARMUP: OpenMP thread[272] instantiated as thread[272]
my_routine():  thread[  0] START_TIME(           2078891848 )
my_routine():  thread[  2] START_TIME(           -528891186 )
...
my_routine():  thread[  2] ENDED_TIME(            635748478 ) sum =  1370488.801186
HOT RUN:    in thread[  2] my_routine() returned                          10.915321 ....
my_routine():  thread[  4] ENDED_TIME(          -1543969584 ) sum =  1370489.030301
HOT RUN:    in thread[  4] my_routine() returned                          11.133672 ....
my_routine():  thread[  1] ENDED_TIME(           -213996360 ) sum =  1370489.060176
HOT RUN:    in thread[  1] my_routine() returned                          11.158897 ....
...
my_routine():  thread[  0] ENDED_TIME(           -389214506 ) sum =  1370489.079366
HOT RUN:    in thread[270] my_routine() returned                          11.149798 ....
my_routine():  thread[  3] ENDED_TIME(           -586400566 ) sum =  1370489.125829
HOT RUN:    in thread[269] my_routine() returned                          11.091430 ....

OpenMP ver(201511)...finito

模型源（在 TiO.run 上）：

#include <omp.h>   // ------------------------------------ compile flags: -fopenmp -O3
#include <stdio.h>

#define MAX_COUNT    999999999 
#define MAX_THREADS        272

double my_routine()
{
     printf( "my_routine():  thread[%3d] START_TIME( %20d )\n", omp_get_thread_num(), omp_get_wtime() );
     double temp = omp_get_wtime(),
            sum  = 0;

     for ( int count = 0; count < MAX_COUNT; count++ )
     {
           sum += ( omp_get_wtime() - temp ); temp = omp_get_wtime();
     }
     printf( "my_routine():  thread[%3d] ENDED_TIME( %20d ) sum = %15.6f\n", omp_get_thread_num(), omp_get_wtime(), sum );
     return( sum );
}

void warmUp() // -------------------------------- prevents performance skewing in-situ
{             // NOP-alike payload, yet enforces all thread-instantiations to happen
    #pragma omp parallel for num_threads( MAX_THREADS )
    for ( int i = 0; i < MAX_THREADS; i++ )
         printf( "WARMUP: OpenMP thread[%3d] instantiated as thread[%3d]\n", i, omp_get_thread_num() );
}

int main( int argc, char **argv )
{
    omp_set_num_threads( MAX_THREADS ); warmUp(); // ---------- pre-arrange all threads

    #pragma omp parallel for
    for ( int i = 0; i < MAX_THREADS; i++ )
         printf( "HOT RUN:    in thread[%3d] my_routine() returned %34.6f ....\n", omp_get_thread_num(), my_routine() );

    printf( "\nOpenMP ver(%d)...finito", _OPENMP );
}

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