Subject: Re: Some questions about NetBSD SMP
To: Miao Qingjun <>
From: Nathan J. Williams <nathanw@MIT.EDU>
List: tech-kern
Date: 02/13/2001 02:17:49
Miao Qingjun <> writes:

> Is NetBSD SMP source code in NetBSD-1.5?


> How many CPUs can NetBSD support on i386 platform?

I believe the current branch of the multiprocessor code has been tested
with as many as six CPUs. I'm not sure what the first bottleneck to
number of CPUs will be. Probably "availability of test hardware". 

> Can different processes on different CPUs
> simultaneously trap into kernel and run in parallel?
> Or is there a big lock whick locks the whole kernel? 

At the moment it's a close approximation to a big lock. A little bit
of infrastructure has been added to mark system calls as needing the
big lock or not, which is a step towards finer-grain locks, but the
only currently non-locking system call deals with read-only
process-specific state.

        - Nathan