[CentOS] Effectiveness of CentOS vm.swappiness

Fri Jun 5 15:40:27 UTC 2015
Greg Lindahl <lindahl at pbm.com>

On Fri, Jun 05, 2015 at 12:29:04PM +0200, Markus "Shorty" Uckelmann wrote:

> How can I further debug this
> problem and find out what's the culprit?

It's working as designed.

Linux does not treat various kinds of memory pages differently. If you
want a daemon to be fully in core, call mlockall(). Here's one way to
do that without changing the daemon's source:

http://superuser.com/questions/196725/how-to-mlock-all-pages-of-a-process-tree-from-console

(I've always only done this with my own code explicitly calling mlock)

If you don't explicitly lock things into memory, file I/O can and will
cause idle pages to get pushed out. It happens less often if you
manipulate swappines.

-- greg