develooper Front page | perl.perl6.language | Postings from February 2001

Re: JWZ on s/Java/Perl/

Dan Sugalski
February 10, 2001 10:51
Re: JWZ on s/Java/Perl/
Message ID:
At 01:05 AM 2/10/2001 +0100, Bart Lateur wrote:
>On Fri, 09 Feb 2001 12:06:12 -0500, Ken Fox wrote:
> > 2. Work proportional to live data, not total data. This is hard to
> >    believe for a C programmer, but good garbage collectors don't have
> >    to "free" every allocation -- they just have to preserve the live,
> >    or reachable, data. Some researchers have estimated that 90% or
> >    more of all allocated data dies (becomes unreachable) before the
> >    next collection. A ref count system has to work on every object,
> >    but smarter collectors only work on 10% of the objects.
>That may work for C, but not for Perl.
>         sub test {
>             my($foo, $bar, %baz);
>             ...
>             return \%baz;
>         }
>You may notice that only PART of the locally malloced memory, gets
>freed. the memory of %baz may well be in the middle of that pool. You're
>making a huge mistake if you simply declare the whole block dead weight.

This is an argument to make PMCs moveable, I suppose. I don't see what the 
problem is in general, though--the pool of base variable structures might 
get somewhat fragmented, but as it's a pool of fixed-sized structures there 
are tricks you can play to make allocation quick even in a fragmented pool.

As for the actual contents of the scalars in %baz, that's no big deal 
either. They can be moved about with impunity, and that's probably where 
most of the space will get taken up anyway...


--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai                         have teddy bears and even
                                      teddy bears get drunk Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About