[GTALUG] optimum swap size

[Gary]

Thank you. My intent (haven't done it yet) is to use mmap() in c++ for a 
very large file (2 gigs). I suspect that the virtual memory technology 
in x86 would simply page in/out file data to/from ram using the least 
recently used algorithm. Would the swap partition size be material here 
or am I worrying unnecessarily.
/gary

On 19-02-27 10:38 AM, 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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