Re: VM ideas (was: Re: TTY changes to 2.1.65)

[David Mentre <David.Mentre@irisa.fr>]

 Hello Rik,

Rik van Riel <H.H.vanRiel@fys.ruu.nl> writes:

> On Thu, 4 Dec 1997, Joerg Rade wrote:

[snip]
> > My own vote for "most worthwhile hardware for memory management"
> > is sub-page protections in the TLB, e.g., 1-KB independently-protectable
> > units withing 4KB or 8KB pages, like the ARM 6xx series.  
> 
> Swapping is mainly slowed down by _latency_ problems. The
[...]
 The interesting point of Joerg is that he see the TLB mecanism as a
more general mecanism than just to solve swapping problems.

> > These features are desirable for a lot of things, including:
[snip]
> >   3. distributed virtual memory, 
> DIPC is out... check your favorite web site...
[snip]

 As I'm a little involved in Distributed Shared Memories (with a PhD ;),
I couldn't let such an opportunity happen without talking. I totally
agree with Joerg. One problems with DSM is that you must track user
memory accesses to maintain coherency. Unfortunatly, fine grain access
like cache line is not available to the average system
programmer. Therefore sub-page protection could be very useful. 

 Regarding DIPC, I think we could improved a little the coherency
protocol. One big advantage of DIPC is that it provide code, and you
can't lie with code. :) I hope I'll have more code in the future to
explain my point of vue in DSM.

 david

-- 
 David.Mentre@irisa.fr -- CAPS research team - Irisa - France
      Personal info: http://www.irisa.fr/prive/mentre/	
  Professional info: http://www.irisa.fr/caps/PEOPLE/David/