Tried and tested SMP model (was: Re: ... blah blah ...)

[Robert Watson]

On Sun, 19 Sep 2004, Julian Elischer wrote:

> >>Furthermore, the SMP issue is a common problem among many FreeBSD
> >>developers whom have told me the same, there is alot of this 
>  >>information all over the
> >>internet. FreeBSD is unable to perform good on multiple CPUs, 
>  >>the fixes are just work arounds.
> 
> What have they told you? SMP in FreeBSD is coming along quite nicely as
> far as I see.. We now have native SMP scaleable threading in the default
> system, and larger and larger parts of the system ara able to take
> advantage of Multiple processors to parallelise their work. 

And our SMP/threading model is hardly unproven -- substantial parts of the
architecture were based on the extensively documented experiences of the
SunOS/Solaris SMP work, Mach SMP, SGI SMP, BSD/OS SMP, Linux SMP, etc.
Many of these systems have demonstrated excellent scalability on SMP and
NUMA systems (some would say: rediculous scalability), as well as make
very effective use of processor affinity.  While the work of re-writing a
kernel to use explicit synchronization is pretty expensive, and work on
the scheduler requires a lot of hard thinking, it's not as though we're
exploring uncharted waters that might contain unidentified monsters.  And
the hardest part of the current SMP work isn't putting in the locking
primitives, it's identifying and adapting the synchronization requirements
of the components, which is work that has to be done regardless of what
actual SMP model is suggested.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Principal Research Scientist, McAfee Research