Re^4: System call doesn't work when there is a large amount of data in a hash

Without seeing your code, it will be very hard to suggest things on how to make it do what you want.

You have discarded all the obvious things that would make it easier, because you say that you really need this.

Ideally, you show us some minimal code that reproduces the problem so that we can run it ourselves. For example, the following could be a start:

#!perl
use strict;
use warnings;

my $memory_eaten = 8 * 1024 * 1024 * 1024; # 8GB, adjust to fit

my %memory_eater = (
    foo => scalar( " " x $memory_eaten ),
);

my $cmd = "foo bar";
system($cmd) == 0
    or die "Couldn't launch '$cmd': $!/$?";
[download]

Updated: Actually make the hash eat memory by creating a loong string

Comment on Re^4: System call doesn't work when there is a large amount of data in a hash Download Code

Replies are listed 'Best First'.
Re^5: System call doesn't work when there is a large amount of data in a hash by Nicolasd (Acolyte) on Apr 29, 2020 at 15:00 UTC
Thanks For this suggestion, it helped a lot! I tried this script and it worked fine on my laptop, put 12 GB of the 16 GB available in hash and system call still works I did got varying results on the Centos 7 (450 GB of RAM), I monitored it also with top, if I saw a memory increase 20 GB, 50 GB, 100 GB, 150 GB and 200 GB all worked fine, didn't see any memory increase either But with 230 GB (more than half of the available) I ran out of memory (Cannot allocate memory), so I need the same amount of memory free than there is in the hash? And only for Centos then? I also made the system call loop for 10 times and the bigger the hash, the slower the system call starts	[reply]
Re^5: System call doesn't work when there is a large amount of data in a hash by Nicolasd (Acolyte) on Apr 29, 2020 at 11:21 UTC
Hi, Thanks for the reply.The big hash is the most essential part, so really can't change that. I didn't add any code because I tried many different system calls on different locations in the large script. A system call always worked if I put it before the hash is loaded, if I do it afterwards, it never starts The code you send, does that hash takes the memory of your variable $memory_eaten? If so, that would be great to test, I will do it now.	[reply]