Date: Thu, 13 Sep 2001 20:12:50 GMT
From: cfedde@fedde.littleton.co.us (Chris Fedde)
Subject: Re: How to preallocate memory for my perl script (UNIX)
Message-Id: <6r8o7.382$Owe.252165632@news.frii.net>

In article <slrn9q1ckj.eec.tadmc@tadmc26.august.net>, Tad McClellan
<tadmc@augustmail.com> wrote:
>Stan Brown <stanb@panix.com> wrote:
>>
>>I beleive that a part of this is because perl has to make many small
>>requests to the OS for emeory, the first time. So I would like to do
>>something, before the first fetch to get perl to request a large chunk of
>>memory from the OS, the undefine whatever is using this memeory, thus
>>making that memory available to perl for reuse.
>>
>>Sugestions?
>
>
>You can preallocate memory:
>
>   my @array;
>   $#array = 1_000_000;  # a million elements
>or
>   my %hash;
>   keys %hash = 1_000_000;  # a million buckets (perldata.pod)
>

While there are often good reasons for holding a large dataset in
memory. There are often alternatives that can use much less memory.
For example processing one row at a time using the DBI::fetchrow_* methods 
rather than loading the whole result using the DBI::fetchall_* into memory just to walk it and then throw it away.

YMMV
chris
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