[CentOS] What is eating up Swap

[John Doe]

From: Stephen Harris <lists at spuddy.org>

> Having pages in swap is not indicative of a problem; what's more
> important is the level of swap _activity_.  See "vmstat" output, for
> example, to determine how much swap activity is occuring.  If that's
> zero then you're not throwing new pages out to swap.

Maybe unrelated but we ran into some NUMA memory allocation per cpu 
problem with our mysql servers.
The swap would be used (up to 100%) while there was plenty of free RAM.
Prefixing mysqld with "numactl --interleave all" seemed to fix it...

JD