Re: Help in DSM design

From: Horst von Brand (vonbrand@sleipnir.valparaiso.cl)
Date: Sat Mar 04 2000 - 10:57:11 EST


"Albert D. Cahalan" <acahalan@cs.uml.edu> said:
> Richard Gooch writes:

[...]

> > Ach! Not another DSM project :-( Don't do it. There's already a DSM
> > implementation for Linux,

> Obviously this is a feature people want.

Right. Can't be done efficiently right now doesn't stop wishing on a star.

> > and besides, you're better off with a message-passing interface.
> > That way application coders can see how costly operations are.
> > Using DSM hides that, resulting in inefficient code.

> Message passing can be more costly! On the hardware I develop for,
> a "message" involves setting up some DMA control data. Distributed
> shared memory has a one-time setup cost, so it is faster for
> frequent access to small bits of data.

Your machines have ESP to know without message passing that a shared piece
of data was changed in the other corner of the room?

> You could really mess up performance by using a message-passing API
> for repeated random access to 8-byte values. Actually, I think the
> break-even point is near 2 kB.

Then don't use message passing for that.

-- 
Horst von Brand                             vonbrand@sleipnir.valparaiso.cl
Casilla 9G, Viņa del Mar, Chile                               +56 32 672616

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/



This archive was generated by hypermail 2b29 : Tue Mar 07 2000 - 21:00:17 EST