[Suggestions] Swappiness

[Arjan van de Ven]

Daniel Qarras wrote:
> Hi!
> 
> I was wondering whether it would be a worthwhile suggestion to mention
> the /proc/sys/vm/swappiness parameters that can be used to avoid
> swapping and thus reduce hdd spinning? See
> http://www.linuxinsight.com/proc_sys_vm_swappiness.html.

this is... a dangerous tradeoff in this respect; because by swapping 
less you also reduce the disk cache memory footprint, so you'll have 
more cache misses... and those go to disk just as much ;)

in principle the standard vm tuning is the "optimal balance"... and 
wouldn't need actual changes.
Now.. practice might be different. You can easily tell btw

run

"vmstat 1"

and you need to look at the SUM of "bi" "bo" "si" "so"

if si/so are 0 already, you're already not swapping...


bi are cache misses effectively; bo is writeouts back to disk of stuff.


I'll talk to our server admin about your 2 suggestions; thanks for those!