[tech] Swapfile on motsugo

Frames oxinabox at ucc.asn.au
Mon Feb 19 12:10:06 AWST 2018


I have given motsugo a swapfile.
(Give the OS a swapfile, OS's love swapfiles)

It is currently a 64Gb swapfile on /scratch, which I don't think is an 
excellent, because I believe that is on a raided local drive.
lvs says there is a 1.86Gb swap logical volume, but that is insanely 
small, for a machine with 24Gb of RAM.

We should stop provisioning machines without swapfiles.
In general a swapfile is good, because it lets memory that isn't being
Ideally the filesystem should be using almost all the unused RAM for a 
disk-readcache, (but I don't know that motsugo has that kinda filesystem),
which is more useful to have in RAM than a bit of memory that hasn't 
been touched in weeks.

My particular use-case today, is that I've made a webapp that loads a 
10Gb machine learnt model.
Now obviously, it only actually needs that model when someone is using 
the app.
Which is likely to be pretty rare.
If the OS is not being dumb, it should thus store that model in SWAP 
most of the time.


We're better off messing with the swappiness than not have a swapfile at 
all.
In the last 20 minutes of so progressively 1Gb has been swapped out.

[*OX]



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