[gpfsug-discuss] swapped_warn event

[Jonathan Buzzard]

On 16/02/2026 11:43, Jan-Frode Myklebust wrote:
> 
> It seems like someone thinks that linux servers should never use any
> swap. This swapped_warn triggers if you've used more than 50 MB of
> swap space.  I find this silly..

That's a polite way of putting it.

Anecdotally, if memory starts to get tight Linux will preventatively 
push pages to swap "just in case", and might never actually use it. 
Consequently having a warning if more than 50MB of swap space is used is 
as useful as a chocolate teapot.

If you are going to warn about swap being used, then it needs to be 
because the kernel was actually shuffling memory between disk and RAM 
not because it pushed some pages to disk just in case.

On an HPC system where the compute nodes are frequently near maximum RAM 
usage all I unsurprisingly have a load of spurious warnings.

> 
> You can tune it using something like "mmchconfig
> mmhealth-gpfs-swap_alert_threshold_kb=2000000 --force", but I wouldn't
> want to pollute my config with such settings.. Maybe just disable it
> using "mmhealth event hide swapped_warn".
> 

I am debating having a script automatically run "swapoff -a ; swapon -a" 
on the nodes if these warnings are seen :-)


JAB.

-- 
Jonathan A. Buzzard                         Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG