getaffinity/setaffinity and cpu sets.

[Daniel Eischen]

On Wed, 20 Feb 2008, Jeff Roberson wrote:

> I have the following api working:
>
> /*
> * Parameters for the level argument to getaffinity.
> */
> #define CPU_LEVEL_SYS   1       /* All system cpus. */
> #define CPU_LEVEL_AVAIL 2       /* Available cpus for which. */
> #define CPU_LEVEL_WHICH 3       /* Actual mask for which. */
>
> /*
> * Parameters for the which argument to {get,set}affinity.
> */
> #define CPU_WHICH_TID   1       /* Specifies a thread id. */
> #define CPU_WHICH_PID   2       /* Specifies a process id. */
> #define CPU_WHICH_SET   3       /* Specifies a set id. */
>
>
> Along with a CPU_CLR, CPU_COPY, CPU_ISSET, CPU_SET, CPU_ZERO for manipulating 
> the sets.
>
> int getaffinity(int level, int which, int id, int cpusetsize, long *mask);
> int setaffinity(int which, int id, int cpusetsize, long *mask);
>
> The get call has a notion of 'level' which allows us to fetch different 
> masks.  The system set is all processors in the system.  The available set is 
> the set of cpus available to the tid/pid in the 'which' argument.  An 
> application would fetch the avail set and then potentially reduce it.
>
> The setaffinity call doesn't have a level because the avail/sys sets are 
> immutable.  You can only set things which can be specified by the which 
> argument.

Everything looks pretty good to me, but if you add the 'level' to
setaffinity(), you might be able to say "run on any ONE of the CPUs
in the cpuset - I don't care which one".

-- 
DE