On Sun, 2004-04-11 at 19:02, Richard Jones wrote:
> On Sun, Apr 11, 2004 at 06:41:53PM +1000, skaller wrote:

> I did some experiments with early versions of pthrlib (see .sig) where
> I tried swapping stacks in and out during context switches using
> mmap(2). 

Would that work with common C++ implementations which
play tricks with the stack for exception handling purposes?

>   Plus it's probably a lot slower
> because you're trashing the disk cache / data cache and TLB on each
> switch.

I don't really understand why the disk cache should be trashed,
at least any more than any other system: if you need backing
store you'll be invoking the VM system any which way .. 

> If you do this you have to be careful not to share data on the stack
> between threads (not normally a problem).

Similar issue in Felix: if you gave a GC for each thread,
you can't share ordinary state data. If you use a global
GC you can, but there may be an impact on overall (and RT) 
performance.

Interesting issue: can you do both at the same time?
And how would you manage it?

Felix certainly allows a GC plus first class C++
objects which are typically using constructor/destructor
memory management for things like strings, and refcounting
for containers, so if you can partition your data then using
multiple memory management systems at once is certainly
possible, but I have no idea what models might exist
for using multiple GC together.. the Ocaml 
collector with 'world stop' incremental collection seems a good
compromise.

-- 
John Skaller, mailto:skaller@users.sf.net
voice: 061-2-9660-0850, 
snail: PO BOX 401 Glebe NSW 2037 Australia
Checkout the Felix programming language http://felix.sf.net



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