Re: Garbage collection (was Re: JWZ on s/Java/Perl/)

[Hong Zhang]

> There are several concurrent GC algorithms that don't use
> mutexes -- but they usually depend on read or write barriers
> which may be really hard for us to implement. Making them run
> well always requires help from the OS memory manager and that
> would hurt portability. (If we don't have OS support it means
> auditing everybody's XS code to make sure they use wrappers
> with barrier checks on all writes. Yuck.)

The memory barriers are always needed on SMP, whatever algorithm
we are using. It more depends on the memory model that Perl is
going to use.

The memory barrier can be easily coded in assembly, or intrinsic
function, such as __MB() on Alpha.

Hong