Re: [RFC] Multiprocessor Control Interfaces

[Robert Love]

On Mon, 2001-12-10 at 15:14, Jason Baietto wrote:

> I'm currently working on adding multiprocessor control interfaces
> to Linux.  My current efforts can be found here:
> 
>    http://www.ccur.com/realtime/oss
> 
> These are clean-room implementations of similar tools that have
> been available in our proprietary *nix for quite some time, and
> so the interfaces have a fair amount of mileage under their belts.
> Note that the scope is somewhat wider than just MP.

Ahh, very neat.  This is a useful tool.

One idea would be to allow users to set CPUs processes _can't_ run on. 
On high-end systems sometimes a CPU is affined to a particular IRQ (say,
network interface).  Another situation is where you bind a RT task to a
given CPU.  In these situations, you want everything else to _not_ run
on the CPUs.  I.e., `run --bind=!1' (note its easy to generate the
bitmask here too, by ANDing the inverse of the given CPU against -1).

At any rate, what is needed most is to standardize on an interface for
these scheduling mechanisms.  I guess its just CPU affinity we have to
go ... since not much progress was made of my (proc-based) method vs.
Ingo's (syscall-based) method, at this point either of the two being
merged would make me happy.

> These services rely upon Robert Love's CPU Affinity patch
> (version 2.4.16-1 was used for testing) which is available here:
> 
>    http://www.kernel.org/pub/linux/kernel/people/rml/cpu-affinity/v2.4/

I assume you have no problems with it ... I think I'd like to add the
change that the CPUs reported correspond to the physical CPU number and
not the logical value we derive.  On x86 this won't make a difference,
but its a proper method I suspect.

	Robert Love