[CentOS] Effectiveness of CentOS vm.swappiness

Fri Jun 5 19:34:18 UTC 2015
Greg Lindahl <lindahl at pbm.com>

On Fri, Jun 05, 2015 at 09:21:43PM +0200, Markus "Shorty" Uckelmann wrote:
> >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.
> So, is a swappiness value of 60 not recommended for servers?

It's probably a fine default. For my most recent purposes, a web-scale
search engine, I locked a ton of daemons into memory with mlockall (on
latency-optimized clusters) and set swappiness to 0 on all clusters
(including batch-optimized clusters.)

This last bit was because I don't expect my systems to ever swap... I
only have a small amount of swap configured to reduce the mayhem
caused by OOMs, and give my home-grown oom daemon (which is locked
into memory, of course) time to open fire on my choice of offending

-- greg