Re: 'out of memory' errors

tom arnall wrote:

i am trying to us a perl application that handles large files (.5GB) in scalar
variables. when i try to 'slurp' one of these files into a variable
(e.g., '$_ = `cat filename`) i get an out of memory error.

You should consider alternative solutions, like processing files line by
line for example. It highly depends on what you are trying to achieve,
but loading half a gig into memory is not something you should do
without having a very good reason for doing so.

is there not some way to get linux to use swap space when physical memory is
exceeded?

It does that by default, assuming you do have swap partitions or files
available. Note that this can be slow, and I assume this is what you
described as a "freeze".

There are many tunable Linux virtual memory parameters you can set via
sysctl interface. You can get a list of them with "sysctl -a | grep vm".
The most useful one is vm.swappiness. You can set it to a number from 0
to 100. 0 means "try not to use swap at all" and 100 - "swap as much as
possible" with all other values in between. You can set it (and other
sysctl options) like this:

# sysctl -w vm.swappiness=60

To preserve settings on reboots, edit "/etc/sysctl.conf".


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