On Sat, 6 Feb 1999, Ignatios Souvatzis wrote:

> On Fri, Feb 05, 1999 at 09:10:23AM -0800, Eduardo E. Horvath wrote:
> > On Thu, 4 Feb 1999, Ignatios Souvatzis wrote:
> > 
> > > > |	CACHESYNC_GLOBAL
> > > > |
> > > > |	as above, but for multi-threaded applications.
> > > > 
> > > > This is identical to CACHESYNC for single CPU machines, or at least
> > > > architectures. However: cgd mentioned (elsewhere) nobody should want this,
> > > > and if yes, that this could be done by STOREBAR (see below),
> > > > application-internal synchronization, and CACHESYNC in all threads. Opinions?
> > 
> > On a multiprocessor machine CACHESYNC_GLOBAL would need to be used in
> > situations where it is necessary to tell other processors to do a
> > CACHESYNC because there are no convenient synchronization points.  For
> > instance, if you have the JIT compiler running on once CPU and the other
> > CPUs are executing already compiled code, when the JIT compiler completes
> > compilation of a code block it will need to inform the other CPUs to flush
> > the appropriate sections of their caches.  Adding some way to tell all the
> > other CPUs to issue a CACHESYNC is problematical and would affect
> > performance, whereas a CACHESYNC_GLOBAL would issue cross-call interrupts
> > or equivalent to all CPUs to flush their caches immediately.
> > 
> > But this is a rather obscure application, and since there really aren't
> > that many JIT compilers, I don't expect it to be used very often.  OTOH,
> > the STOREBAR and LOOKASIDE would probably be used much more often for
> > spinlocks, etc.
> 
> So, what does should I do?
> 
> I understand the question is academic, as long as we do not have SMPs...
> on our m68k machines, we'll just have CACHESYNC_GLOBAL == CACHESYNC.

Just make CACHESYNC_GLOBAL execute the same code as CACHESYNC until we
have SMP support.  Then CACHESYNC_GLOBAL can be implemented correctly on
those architectures where it's required.

=========================================================================
Eduardo Horvath				eeh@one-o.com
	"I need to find a pithy new quote." -- me