[GTALUG] optimum swap size

[Dave Collier-Brown]

Linux is somewhat unusual in that it dynamically kills large processes when it's running out of memory. You used to have to set limits to get that behavior.   Because of it, I run a moderately large swap (~8 GB) and can watch large jobs drive swap usage up. Then I decide if I want them dead.

--dave

On 2019-02-27 10:38 a.m., Stewart C. Russell via talk wrote:

On 2019-02-27 10:02 a.m., Gary via talk wrote:


I have kubuntu 18.04 with 20 gigs ram. Does anyone know what the optimum
size swap area that I should have?



I asked a question about this at a GTALUG Q&A a few years back.
Basically what I remember was:

* are you frequently running out of memory? If not, don't change anything.

* depending on what applications you're running, there are various
kernel parameters that govern swap behaviour. They're tuned for
"typical" performance.

* The OOM killer (out-of-memory process killer) can sometimes kill a
task that's taking up what it thinks is too much memory. I sometimes get
that with very large (or very badly thought out) OpenSCAD renders, and
it can be annoying to have to work round it. OOM killer exists to keep
the system stable, and doesn't care if your work isn't happening.

Swap is more of a thing on smaller machines such as a Raspberry Pi.
These days, you've always got enough memory + swap until you find that
one job for which you don't. For me, that was trying to build MySQL (for
someone else, I promise!) on a Raspberry Pi.

cheers,
 Stewart


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--
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
dave.collier-brown at indexexchange.com<mailto:dave.collier-brown at indexexchange.com> |              -- Mark Twain



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