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

Mark Hahn hahn at mcmaster.ca
Mon Feb 9 22:01:48 PST 2015

> Any time you touch swap you need to consider both
> overcommit_memory
> overcommit_ratio

no.  when overcommit_memory is default, you can ignore ratio.
when it's 2, then you need to touch ratio if your /proc/meminfo:CommitLimit
is not sufficient to your needs.  running in this mode is not very 
predictive of whether you'll actually touch swap.

yes, it's a bit odd that limit=swap+ratio*ram,
since most people at first thought think limit=ram+ratio*swap.

incidentally, if you run in overcommit_memory=2, the primary memory
metric you should be monitoring is CommitLimit-Committed_AS
("uncommitted memory" - ie, VM available for allocation.)
(fwiw, #1 linux newbie mistake is to ever look at /proc/meminfo:MemFree)

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