On Fri, 7 Sep 2001, Chris Fedde wrote:
> On Fri, 7 Sep 2001 16:58:32 -0400 Michael G Schwern wrote:
> +------------------
> | On Fri, Sep 07, 2001 at 02:32:51PM -0600, Chris Fedde wrote:
> | > Find below recent patches to the FAQ derived from postings to usenet CLPM.
> | > Is there a better place I should be posting these?
> |
> | > +If you need to initialize a large variable in your code, you
> | > +might consider doing it with an C<eval> statement:
> | > +
> | > + my $large_string = eval ' "a" x 5_000_000 ';
> | > +
> | > +This allows perl to immediately free the memory allocated to the
> | > +eval statement, but carries a (small) performance penalty.
> |
> | Does this really work?
> +------------------
>
> Apparently.
>
> cat t
> my $large_string = eval ' "a" x 5_000_000 ';
> print "holding\n";
>
> ps -axo pid,rsz,vsz,tsiz,command | grep perl
> 47904 3692 4188 656 perl -d t
>
> cat u
> my $large_string = "a" x 5_000_000;
> print "holding\n";
>
> ps -axo pid,rsz,vsz,tsiz,command | grep perl
> 47907 13476 13960 656 perl -d u
>
> uname -a
> FreeBSD fedde.littleton.co.us 4.4-RC FreeBSD 4.4-RC #16: Sat Aug 18
> 13:46:32 MDT 2001
> [EMAIL PROTECTED]:/home/usr.obj/home/usr.src/sys/FEDDE i386
If you want to test memory GTop is a killer (if you can get libgtop
compiled on your platform :(
On linux (ker-2.2.19/libc-5.3.12/def malloc) it releases only a part of
the allocated memory (about a half?):
% perl
use GTop;
my $gtop = GTop->new;
print "before ", GTop::size_string($gtop->proc_mem($$)->rss), "\n";
my $large_string = "a" x 5_000_000;
print "normal ", GTop::size_string($gtop->proc_mem($$)->rss), "\n";
my $large_string1 = eval ' "a" x 5_000_000 ';
print "eval ", GTop::size_string($gtop->proc_mem($$)->rss), "\n";
before 2.2M
normal 11.7M
eval 16.5M
(this is with 5.6.1 and similar with 5.7.1)
_____________________________________________________________________
Stas Bekman JAm_pH -- Just Another mod_perl Hacker
http://stason.org/ mod_perl Guide http://perl.apache.org/guide
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