On Monday 21 April 2008 21:47:21 Richard Jones wrote:
> On Mon, Apr 21, 2008 at 03:44:08PM +0100, Jon Harrop wrote:
> > On Monday 21 April 2008 14:11:51 Richard Jones wrote:
> > > Your threaded code is going to look really stupid when you have NUMA
> > > machines with dozens of cores.  Why are we optimizing for a case (SMP)
> > > which will only be around for a few years.  Arguably SMP isn't even
> > > around now ... the AMD machine on which I'm typing this is firmly NUMA
> > > with a good 10% penalty for accessing memory owned by the other
> > > socket.
> >
> > 10% is nothing compared to the orders of magnitude cost of message
> > passing.
>
> Or you could use shared memory (as I said below).

As we recently quantified, that is also 100x slower without a concurrent GC.

> > > > A concurrent GC should be developed.  But I think you can compete in
> > > > some "niches" without a concurrent GC.
> > >
> > > Why should a concurrent GC be developed?  Threaded code is a nightmare
> > > to write & debug, and it's only convenient for lazy programmers who
> > > can't be bothered to think in advance about how they want to share
> > > data.  OCaml supports fork, event channels & shared memory right now
> > > (and has done for years) so there is no penalty to writing it
> > > properly.
> >
> > Ten years ago that was:
> >
> >   "Why should we use gargage collection? Garbage collectors are a
> > nightmare to implement and debug and are only useful for lazy programmers
> > who cannot be bothered to deallocate values themselves. C++ has reference
> > counting right now and there is no penalty for using it properly."
>
> Thanks for the straw man argument there.  Garbage collectors and _not_
> using threads both improve the safety of the language.

Avoiding threads does not improve the safety of the language, it simply 
degrades the capabilities of the language.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/?e