1. Introduction

The previous article discussed how to check process priority; this one explains how to set process priority.

There are two methods for setting process priority:

1. Command line;
2. Source code;

2. Command Line Method

main.c:

#include <stdio.h>

int main(int argc, char *argv[])
{
    while(1)
    {
        ;
    }

    return 0;
}

Compile:

gcc -o proc-pri main.c

To conveniently check the priority, I use the <span><span>top</span></span> command.

2.1 Normal Processes

2.1.1 Set Priority When Starting a Process

sudo nice -n [nice value] [application]

Test:

2.1.2 Modify Priority of Running Process

sudo renice -c [nice value] [application pid]

Test:

2.2 Real-Time Processes

2.2.1 Set Priority When Starting a Process

sudo chrt -f [priority] [application]

-f: Set the process scheduling policy to SCHED_FIFO;

-r: Set the process scheduling policy to SCHED_RR.

Test:

2.2.2 Modify Priority of Running Process

sudo chrt -fp [priority] [application pid]

Test:

3. Source Code Method

3.1 Normal Processes

int nice(int inc);

main.c:

#include <stdio.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
    nice(-15);

    while(1)
    {
        ;
    }

    return 0;
}

Test:

3.2 Real-Time Processes

#include <pthread.h>
int pthread_setschedparam(pthread_t thread, int policy, 
                          const struct sched_param *param);

Test:

4. Conclusion

If you need to modify the priority of a certain program, you can first use the command line method for testing, and once the test is stable, you can solidify the priority in the code.