Re: Lets get this right (WAS RE:MOSIX and kernel mods)

Richard Gooch (rgooch@atnf.csiro.au)
Sun, 7 Mar 1999 21:22:40 +1100

Larry McVoy writes:
> : Sounds good for the different processes case. But I was thinking of
> : the shared VM case (threads), where you don't (ideally) even have to
> : do that.
> :
> : Perhaps the best approach is to define extended send semantics to
> : "send and I don't mind if my buffer is modified". That would be much
> : simpler than stuffing around in the VM layer to do all kinds of
> : tricks. Tricks that probably won't work in a shared VM environment
> : anyway.
>
> Yes, except that those semantics aren't what people are willing to
> accept.

Which kind of proves my point about one size doesn't fit all...

> And the tricks work just fine in a shared VM - you can mark anything
> copy on write. Besides, SGI uses sproc() for threads (an early
> version of clone() ).

Erm, how does that work? The models I've seen for threads is that all
VM is the same for all threads. Having COW pages such that one thread
ends up seeing different contents than another breaks that model.

Yeah, I know about sproc(): that's what I use for my IRIX port (had
to: IRIX didn't have POSIX threads back then). It's a pity about all
the stuffing around you have to do with arenas and usconfig(),
though.

Regards,

Richard....

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