RPI3 swap experiments

[Trev]

bob prohaska wrote on 30/06/2018 01:51:
> On Fri, Jun 29, 2018 at 10:28:25PM +1000, Trev wrote:
>>
>> Jun 29 20:20:35 rpi3 kernel: pid 66844 (c++), uid 0, was killed: out of
>> swap space
>>
>> At the time of "out of swap" only 157M of the 4G swap was in use. The
>> 4GB swap partition is on a 4GB USB2 memory key (da1p1), everything else
>> is on the sdcard. There are no excessively long ms/w being recorded.
>> There are no USB or other related errors.
>>
> 
> That's a little surprising, and disturbing. By my experience your setup
> should have run to completion.
> 
> Do you see a "too much swap" complaint? I don't know if it's a problem,
> but 4 GB of swap triggers one on my RPi3. 3 GB does not. 2 GB is enough
> to finish -j4 buildworld.

Indeed, yes:

warning: total configured swap (1035254 pages) exceeds maximum 
recommended amount (921968 pages).
warning: increase kern.maxswzone or reduce amount of swap.

(I get a similar warning for the RPi2B which has 2GB of swap, but uses 
1.4G+ peak during a -j4 buildworld and always completes successfully.)

I'll reduce it to 2G and see what happens in 5 hours...