[Beowulf] [OOM killer/scheduler] disabling swap on cluster nodes?

Joe Landman landman at scalableinformatics.com
Tue Feb 10 11:11:27 PST 2015

On 02/10/2015 02:02 PM, Mark Hahn wrote:


> is net-swap really ever a good idea?  it always seems like asking for
> trouble, though in principle there's no reason why net IO should be
> "worse" than disk IO...

... except for the need to allocate memory to build packets to send the 
swap data.

I've not done it recently (in the last few years), but previously, 
network based swap was a recipe for a death spiral.

If you can use zram, use it.  If you can't, decide if swap is important 
(HPC no, VMs possibly, other use cases vary).

There are still a few places that look at you funny if you suggest 
running w/o swap.  The 6 orders of magnitude performance difference for 
random page touching performance suggests you should stare them back down.

Seriously, if you can avoid under-spec'ing/provisioning ram, you should. 
  Not everyone can, so you may need it.  Just understand that when it 
hits, you may wish for the wild west of OOM shooting random things in 
comparison to random 4k page touches.  Yes, I've seen the latter.

Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics, Inc.
e: landman at scalableinformatics.com
w: http://scalableinformatics.com
t: @scalableinfo
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