05-17-2013
This is a recurring stress dream from the pre-UNIX, pre-MULTIX O/S including many IBM O/S. UNIX dies of low swap space, but low RAM is quite desirable (you paid for it, so sw that uses it all, all the time is great), since it is a cache for things on disk. When a process exits, it creates some free pages from freed swap or could-swap-but-swap-never-allocated pages, but mmap() pages like linked dynamic libraries remain in RAM awaiting other mmap() of the same file, like libc.so. If lots of stuff ends and nothing new runs, the free RAM may be substantial and persistent, but it just says you are not using the RAM and the whole machine fully, in ways that exploit the RAM you bought. Just booted systems can be a bit slugish as RAM pages get written from disk, then perk up as more of the pages needed for each new process are already in RAM. A process that mmap()'s files and reads them in excess can roll every other app's pages from RAM, a vulnerability; when it stops, they all gradually return to full responsiveness as they roll in their pages.
Some O/S map swap and /tmp together, so either files in /tmp or many programs malloc()ing lots of space (new'ing objects) can draw down the swap space to dangerous levels. You can make more swap using any local files space using mkswap or the like, in an emergency, but usually the trick is to kill the hog. Sometimes a programmer needs to do things in file space or with mmap() not malloc(), or needs to not run 983 parallel processes, but 32 at a time until all are run (I like 2x the CPU Core count, assuming 50% i/o bound processing). Disk is so cheap, so not being stingy on swap is a great direction, too. Fussing over lack of VM is not worth your time.
Last edited by DGPickett; 05-17-2013 at 04:07 PM..
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LEARN ABOUT DEBIAN
matcherrc2perlfilter
MATCHERRC2PERLFILTER.PL(1) User Contributed Perl Documentation MATCHERRC2PERLFILTER.PL(1)
NAME
matcherrc2perlfilter -- Conversion of matcherrc rules to perl
DESCRIPTION
This script converts matcherrc filtering rules into perl_filter rules for usage with the claws-mail-perl-filter plugin of the Claws Mail
mailer.
USAGE
matcherrc2perlfilter
No arguments required. Conversion is done for current user only.
FILES
$HOME/.claws-mail/matcherrc
Input file where standard filtering rules lie.
$HOME/.claws-mail/perl_filter
Output file written by this script. Converted rules are appended if the file already exists, so be careful when running the script more
than once.
BUGS
This conversion script doesn't produce nice Perl code and is just intended to get you started. If you choose to use the Perl plugin,
consider rewriting your rules.
SEE ALSO
claws-mail-perl-filter(1), claws-mail(1)
AUTHOR
This manual page was written by Ricardo Mones <mones@debian.org>, for the Debian GNU/Linux system (but may be used by others). The
matcherrc2perlfilter was written by Holger Berndt <berndth@gmx.de>.
perl v5.14.2 2012-11-17 MATCHERRC2PERLFILTER.PL(1)