RPI3 swap experiments

[Rodney W. Grimes]

> On Tue, Jul 31, 2018 at 10:31:33PM +1000, Trev wrote:
> > bob prohaska wrote on 31/07/2018 15:47:
> > 
> > > It would be most interesting to see what happens if OOMA
> > > could be turned off. Is that possible?
> > 
> > Possibly, but you might find you're treating the symptom(s) rather than 
> > the cause(s) ... something must be triggering the condition whether 
> > correctly or not.
> 
> That's my point. To determine if OOMA is triggered correctly or not. I'm starting
> to think not.
> 
> The reason is the dependency on swap layout (mixed USB/microSD vs all one or the
> other) and the fact that OOMA kills don't seem to coincide with periods of 
> maximum storage read/write delay, which is the conventional explanation for
> why OOMA kills happen in the first place. If turning off OOMA allows buildworld
> to complete successfully it suggests OOMA isn't correctly implemented. 
> 

An easy way of triggering OOM that I ran accross the other day is simply:
truncate -s 4G foo
grep Anything foo

grep(1) well gladly grow up to 4G trying to create a "line" of text
to search for the string "Anything".  On a system with less than
4G of free memory this triggers an OOM and starts killing processes.

Probably has to be run as root or limits get hit.


-- 
Rod Grimes                                                 rgrimes at freebsd.org