Intentionally using a certain amount of memory using a perl script
I need to simulate a hungry process. For example, on a 4.0 GiB machine, I need a process that will consume 3.2 gigabytes (give or take some MiB).
I assumed it should be that simple:
my $mbytes = 3276;
my $huge_string = 'X' x ($mbytes * 1024 * 1024);
But in the end, I end up with twice as much memory as I need.
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it's the same on two windows 7 amd64 computers, one with 64-bit, the other with 32-bit Strawberry Perl build
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I am using Sysinternals Process Explorer and looking at "Private Bytes"
Of course, I could have just $mbytes /= 2
(at the moment I will probably do this), but:
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Is there a better way?
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Can anyone explain why the sum is twice the length of the string?
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Code adapted from http://www.perlmonks.org/index.pl?node_id=948181 , all credit goes to Perlmonk BrowserUk .
my $huge_string = 'X';
$huge_string x= $mbytes * 1024 * 1024;
why is the sum twice the length of the string?
Think about the evaluation order. The correct expression allocates memory for your expression x
, and again the assignment operation to your new scalar. As usual for Perl, although the right-hand expression is no longer mentioned, the memory is not immediately freed.
Working on the existing scalar avoids the second selection as shown above.
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