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Date: Wed, 10 Oct 2012 09:55:29 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: peflags makes perl not print to stdout
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On Sep 24 17:29, Saurabh T wrote:
> 
> I have been trying to get perl to use 2GB of memory (this is on a 32 bit xp machine with 4 GB total memory). As per http://cygwin.com/cygwin-ug-net/setup-maxmem.html I tried 
> peflags --cygwin-heap=2048 /usr/bin/perl

This can't work.  Regardless of your physical memory installed, the
virtual memory is restricted to 2 Gigs per process, unless you use the
methods described in
http://msdn.microsoft.com/en-us/library/bb613473%28VS.85%29.aspx

But even then, the virtual memory layout of a 32 bit process (image,
stack, heap, DLL placement) is so that you won't get more than about 1
Gig of heap, even if you booted the system in /3GB mode.

Have a look into /proc/$PID/maps, it's quite instructive.  It's very
simple with less:

  $ less /proc/self/maps

> However this causes perl to not write to screen.
> On further investigation, I found the magic number to be 1040:
> 
> $ peflags --cygwin-heap=1039 /usr/bin/perl
> /usr/bin/perl: initial Cygwin heap size: 1039 (0x40f) MB
> 
> $ perl -e 'print "Hello\n";'
> Hello
> 
> $ peflags --cygwin-heap=1040 /usr/bin/perl
> /usr/bin/perl: initial Cygwin heap size: 1040 (0x410) MB
> 
> $ perl -e 'print "Hello\n";'
> 
> $
> 
> In other words, anything 1040 and above, perl stops writing to screen.
> I have the latest cygwin (1.7.16) and perl (5.14.2).
> Any idea what might be wrong? Thank you.

I can't reproduce this, even with --cygwin-heap=2048.  While Cygwin
tries to allocate such a heap, it will fallback to a smaller heap
if that's not possible.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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