Speeding up GC

[Andi Kleen]

Richard Henderson <rth@redhat.com> writes:

> A better way to do this is to actually compact the GC arena
> and mark the pages read-only.  If the objects are modified,
> the SIGSEGV handler marks the page read-write again and flags
> the page as having been modified.

Unfortunately changing pages to read only and back is rather expensive.
Cheaper would be to expose the hardware's page dirty bit to user space
and use it for this. Apparently some OS like Solaris support it already
(at least that is what the relevant function in the boehm-gc suggest) 
I guess it could be added to Linux too.

-Andi