From: Eric Mahurin <eric_mahurin@...>
Date: 2005-10-06T01:02:54+09:00
Subject: Re: Concerning shared flag

Not sure if you are aware or not, there are some serious
performance (run-time and memory) issues with element sharing
in the current ruby.  Try any method that takes a small slice
of a large array and then later (even after the small slice is
GCed) modify the large array.  The modify will cause a copy of
the large array and the small slice will continue to reference
the original large array.  You can see how this could cause
serious run-time and memory penalties.

I've done a patch to fix this plus do other speedups.  See the
thread "another array patch - massive performance boosts".

I'd suggest you not do element sharing in your custom class
until this is resolved.

I agree that it would be nice if the GC was more generalized to
let the class handle these special cases (element sharing)
instead of embedding this code in gc.c.

--- Christophe Poucet <christophe.poucet@gmail.com> wrote:

> Hello,
> 
> I'm trying to build an object that behaves just like Array in
> c. However
> there seems to be one stumbling block. I looked at the
> garbage collector and
> there is no special case in T_DATA in case an object has the
> flag shared. I
> think there should be two different marking functions in case
> an object has
> the set and in the case it does not. That way I could design
> something like
> this:
> struct RVarArrayData {
> long len;
> union {
> long capa;
> VALUE shared;
> } aux;
> VARVALUE * ptr;
> };
> 
> However at the moment this is not a possibility.
> 
> With regards,
> Christophe
> 



		
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