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Date:	Thu, 31 Dec 2009 11:36:59 +0000
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Subject:	Re: Is there anyway to reduce cygwin perl's String memory usage?
From:	Reini Urban <rurban AT x-ray DOT at>
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2009/12/30 Zhao, Dong:
> Dear All:
> Recently our Perl project run into the "Out of memory" issue on Windows C=
ygwin, while it works well on Linux, after optimized the code ,it still did=
n't work on Windows Cygwin perl(Because we do a lot of analysis bases on st=
ring arrays and hashes) . We found the reason is Cygwin perl uses much more=
 memory than Linux perl or Windows As perl.
> We did a lot searches over the internet but didn't found a solution yet.
> I did tune the =A0"heap_chunk_in_mb" flag to "2048" =A0in registry "Softw=
are/Cygnus Solutions/Cygwin/". But our Perl script still exhausted over 1GB=
 memory and crashes on Cygwin perl.
>
> Then I compared the memory usage difference between Cygwin perl, Windows =
AS perl, and Linux Perl use this simple script:
>
> =A0=A0=A0 my @array =3D ();
> =A0=A0=A0 my $str =3D "A" x 1024;=A0 #A string with 1024 len
> =A0=A0=A0 for(my $i=3D0;$i<100*1024;$i++){
> =A0=A0=A0=A0=A0=A0=A0 push @array,$str;
> =A0=A0=A0 }
> =A0=A0=A0 <STDIN>; #No we can take a look at memory.
>
> I expected it to use about 100M memory for all platforms. But Windows cyg=
win perl use about 200M, while AS perl and Linux perl only used 100M.
> Our current cygwin perl version is v5.10.0. And cygwin version is 1.7.1.
> I also tried the latest cygwin perl version : v5.10.1. But still the same=
 result.
>
> Can anyone explain to me?=A0 It there a simple way to reduce the cygwin p=
erl's memory usage(Set some flag?Or recomple cygwin perl code)
> Thanks for any answer!

I 'll investigate. Best is always to pre-allocate huge memory to help
those malloc calls.

We are using the standard perl malloc -Dusemymalloc=3Dy (hints/cygwin.sh)
Maybe the other platforms are using their system malloc.

You can override that with -Dusemymalloc=3Dn

../perl-5.10.1/Configure -de -Dlibperl=3Dcygperl5_10_sysmalloc.dll
-Dmksymlinks -Dusethreads -Dmad=3Dy -Dusemymalloc=3Dn
(untested)
--=20
Reini Urban
http://phpwiki.org/           http://murbreak.at/

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