Re: [rvm-research] Jikes Code Cache Management

Michael Bond <[email protected]> wrote on 05/08/2013 04:53:32 PM:

>
> By default, USE_CODE_SPACE is true, and (machine) code is allocated into
> special code spaces that are non-moving spaces. However, if
> USE_CODE_SPACE is false, then it looks like code is allocated into the
> default space, which could be a moving space. Assuming that's right,
> then I'm not entirely sure how pointers to code are updated. At least
> some calls are indirect: they go through TIBs (virtual dispatch) or the
> JTOC (static methods), so just updating these tables is sufficient. Are
> all calls indirect, or are there direct calls in the code that need to
> be updated by updating pointers in the code itself? I suspect that all
> calls are performed indirectly rather than having absolute hard-coded
> callee addresses in the code.
>

Independent of USE_CODE_SPACE, all calls in Jikes RVM are indirect. (even
static calls indirect through the JTOC).  On the plus side, this makes
adaptive recompilation very simple (install a new version of the code
simply by updating a TIB/JTOC pointer).  On the minus side, we are likely
losing at least some performance by indirecting on every call.

I'd started working on implementing support for direct (pc-relative) calls
back at OOPSLA'07 in Montreal, but never completed it.  I still have a
patch set kicking around if anyone wants to take another run at it.  I
figured it was going to take me a month +/- of solid work to make all the
needed changes (pc relative calls on both platforms, still supporting GC of
code, adaptive recompilation, etc).

--dave

------------------------------------------------------------------------------
Learn Graph Databases - Download FREE O'Reilly Book
"Graph Databases" is the definitive new guide to graph databases and 
their applications. This 200-page book is written by three acclaimed 
leaders in the field. The early access version is available now. 
Download your free book today! http://p.sf.net/sfu/neotech_d2d_may

_______________________________________________
Jikesrvm-researchers mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/jikesrvm-researchers