Re: Thread scheduling on an SMP

["Richard Nairn" <Richard@nairnconsulting.ca>]

If I am reading your question correctly, you are talking about schedular  
affinity. You can set which processors you would like to assign pid's to.  
You need a kernel after 2.5.8 for thiese functions...

Excerpt:

#include <sched.h>

int sched_setaffinity(pid_t pid, unsigned int len, unsigned long *mask);

int sched_getaffinity(pid_t pid, unsigned int len, unsigned long *mask);

DESCRIPTION
sched_setaffinity sets the CPU affinity mask of the process denoted by  
pid. If pid is zero, then the current process is used.

The affinity mask is represented by the bitmask stored in mask. The least  
significant bit corresponds to the first logical processor number on the  
system, while the most significant bit corresponds to the last logical  
processor number on the system. A set bit corresponds to a legally  
schedulable CPU while an unset bit corresponds to an illegally schedulable  
CPU. In other words, a process is bound to and will only run on processors  
whose corresponding bit is set. Usually, all bits in the mask are set.

The argument len is the length of the data pointed to by mask. Normally  
this is the size of a word on the system. For compatibility with future  
versions of the Linux kernel, since this size can change, the bitmask  
supplied must be at least as large as the affinity mask stored in the  
kernel.

The function sched_getaffinity writes into the pointer supplied by mask  
that is size len the affinity mask of process pid. If pid is zero, then  
the mask of the current process is returned.

On Thu, 23 Dec 2004 10:14:17 -0300, Darío Mariani  
<mariani.dario@gmail.com> wrote:

> Hello:
>   I have a machine with 4 processors, and I wold like to make the
> following: Set 1 processor to do general stuff using the default
> scheduler and the other three working on my program exclusively, with
> the realtime or my own thread scheduler.
>   Is this possible?, thanks for any comment or links to documentation
> you can give me.
>
>               Darío
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