Re: 2.6 must-fix list, v2

Shaheed R. Haque
2003-05-13T22:33:46Z

Quoting Andrew Morton <akpm@digeo.com>:

> "Shaheed R. Haque" <srhaque@iee.org> wrote:
> >
> > - Add ability to restrict the the default CPU affinity mask so that
> > sys_setaffinity() can be used to implement exclusive access to a CPU.
>
> Why is this useful?

Because it allows one to dedicate a CPU to a process. For example, lets say you
have a quad processor,and want to run joe-random stuff on CPU 0, but a
specialised program on CPUs 1, 2, 3 that does not want to compete with
joe-random stuff.

With sys_setaffinity(), one can set the affinity of the special program to
0xe...but the default affinity for all the joe-random stuff is still 0xf (from
cpu_online_map)! Since its impractical to to modify every single joe-random
executable to set its affinity to 0x1, a way is needed to set the default. The
logical place is in init(), a.k.a. kernel/fork.c.

I hope that make sense.

Thanks, Shaheed