Computing system memory in use in Perl

Question

I followed the top answer here, see below for code to get system memory being used at a given line in my perl code. I'm running Windows 7 Home Basic, 64 bit, 4 GB ram, 4.06 GB Virtual memory (As specified under advanced system settings under My computer). I got following message from perl at a line, before perl goes Out of Memory.

Memory usage: 1916346368

Assuming that this number is in bytes (= 1.78 GB), why did perl go Out of Memory? How can I get system total memory usage by all the processes?

Code block to compute memory is as below. I'm using Strawberry Perl 5.12.3.0

use Win32::OLE qw/in/;

sub memory_usage() {
    my $objWMI = Win32::OLE->GetObject('winmgmts:\\\\.\\root\\cimv2');
    my $processes = $objWMI->ExecQuery("select * from Win32_Process where ProcessId=$$");

    foreach my $proc (in($processes)) {
        return $proc->{WorkingSetSize};
    }
}

print 'Memory usage: ', memory_usage(), "\n";

Perl -V gives following info http://pastebin.com/mvF7YgKH

Update: The problem got solved with 64 bit perl. But I also noticed that the program ran w/o hitch on 32 bit perl on Ubuntu. So, may be Strawberry perl on Windows takes more memory than perl on Ubuntu.

Answer 1

If you were trying to allocate, or reallocate, an enormous string, array or hash it could have requested a larger memory block than was available from the system. While you have 4 gigs of real memory and 4 gigs of virtual, other processes might have been consuming a large chunk of that.

Alternatively, your system might have a per process memory limit which would might be 2 gigs.

Finally, your OS may be 64 bit, but your Perl may be 32 bit. In that case the maximum amount of memory it can address would be 2 gigs. If you post a copy of perl -V somewhere we can view we might be able to work that out.

Answer 2

You have 32-bit Perl. It is not surprising that Windows cannot allocate more than 2GB or memory to 32-bit process. If you install 64-bit Perl, this should max out at physical RAM.