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Operating Systems Linux How execute exactly one process? Post 302848091 by jim mcnamara on Wednesday 28th of August 2013 12:46:29 PM
Old 08-28-2013
This can be a terrible idea, but this is how you do it.

Logon as root. Then try to set your process to a very high priority, thus avoiding the scheduler.

One way is -- Use the nice command as a workaround. Also: in Linux there are ways to create realtime priority classes for processes. To determine the highest realtime priority you can set programmatically, make use of the sched_get_priority_max function. Also be aware: MAX_USER_RT_PRIO is the priority user space should ever run in. Period. See sched.h

On Linux 2.6.32 a call to sched_get_priority_max(SCHED_FIFO) returns 99.
Consider reading this
Real-Time Linux Kernel Scheduler | Linux Journal



nice Example:
Login to root
Code:
a=( nice -19  && ./myprocess)

Logout of root.

If timing is such a big deal you should consider synchronization primitives: mutexes, semaphores, locking.

If your code is running as root you can use the nice() syscall to accomplish priority changes as well.


Note: If your process is having a problem it can bring the whole system to its knees.

Since you do not seem to know about process priority I would suggest that other mechanisms be tried first, before nice(). Meaning: Because you are asking this question, it would appear you may not be experienced enough to do realtime coding.
 

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nice(3) 						     Library Functions Manual							   nice(3)

Name
       nice - set program priority

Syntax
       int nice(incr)
       int incr;

Description
       The scheduling priority of the process is augmented by incr.  Positive priorities get less service than normal.	Priority 10 is recommended
       to users who wish to execute long-running programs without flack from the administration.

       Negative increments are ignored except on behalf of the super-user.  The priority is limited to the range -20 (most urgent) to 20 (least).

       The priority of a process is passed to a child process by For a privileged process to return to normal  priority  from  an  unknown  state,
       should  be  called successively with arguments -40 (goes to priority -20 because of truncation), 20 (to get to 0), then 0 (to maintain com-
       patibility with previous versions of this call).

Environment
       In any mode, nice returns -1 and sets on an error.  On success, the return value depends on the mode in which your  program  was  compiled.
       In  POSIX  or  System V mode, it is the new priority; otherwise, it is zero.  Note that, in POSIX and System V mode, -1 can indicate either
       success or failure; must be used to determine which.

See Also
       nice(1), fork(2), setpriority(2), renice(8)

																	   nice(3)
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