FreeBSD 10 swapping Idle processes :/

[RW]

On Wed, 30 Jul 2014 19:14:57 -0400
Allan Jude wrote:

> On 2014-07-30 17:24, Adi wrote:
> > Hello
> > 
> > i7-4770 , 32 GB RAM,  FreeBSD 10.0-RELEASE-p7,  AMD64, UFS2
> > 
> > Problem: Many idle processes is swapping :(
> > 

> 
> That looks odd, the output of top shows 0 swap usage, but also 0
> resident memory for most of the processes...
> 

My guess would be that these processes have had all their pages
deactivated to accelerate their paging-out. Linux uses the terms
swapping and paging interchangeably to mean paging. In FreeBSD
swapping refers to the management of paging at the process level - in
some cases it's more efficient to page-out all the memory from some
idle or less active processes. 

I did think swapping was only used under abnormal memory shortage, but
I just reproduced this by dd'ing a 16 GB file to tmpfs (with 16GB RAM,
and 16GB swap). Some processes were marked as swapped before any
actual paging occurred.