How to set that a particular thread always be executed by a specific core in multi-core Linux environment?

Question

As we heard of terms like multi processor and multi core system

Both are same or some difference exist between them ??

Answer 1

See the following snippet to set the particular thread to particular core..

    core = CORE_2;                                                       
    cpu_set_t cpuset;                                                           
    pthread_t thread;                                                           
    thread = pthread_self();                                                    
    CPU_ZERO(&cpuset);                                                          
    CPU_SET(core, &cpuset);                                                     

    ret = pthread_setaffinity_np(thread,                                        
              sizeof(cpu_set_t), &cpuset);                                                   
    ret = pthread_getaffinity_np(thread,                                        
            sizeof(cpu_set_t), &cpuset);                                        

    if (CPU_ISSET(core, &cpuset))                                               
        printf("CPU [%d]\n",core);                              

Comments

Hi Jaganathan,

Where is this macro 'CORE_2' defined? Also, what data type is variable 'core'?

Regards

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Hi Jaganathan,
can you give example clearly, I am a begginer.

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Hi upayan

Core is integer variable, CORE_2 is user defined value of particular core number. It start from 0 to N number of core

Hi mohan,

After creating a thread you can set this property any time.

Answer 2

Elaborating Jaganathan's reply:

The header file to include is sched.h, for using CPU_ZERO and CPU_SET macros.
If I am right the #define _GNU_SOURCE macro should also be defined.

cpu_set_t is a bitset where each bit represents a CPU. How the system’s CPUs are mapped to bits in the bitset is system dependent. To manipulate this bitset, to set and reset bits, a number of macros are defined:
CPU_ZERO, CPU_SET, CPU_CLR etc.

The pthread_setaffinity_np, as its already understandable, sets the affinity of thread to the cpuset defined above using CPU_SET macro.

Regards,
Upayan.