Buildworld seems to have slowed lately

[bob prohaska]

On Tue, Jun 25, 2019 at 09:35:06AM +0200, Daniel Engberg wrote:
> 
> Without details it's a bit hard to give you any suggestions but for 
> instance a new version of llvm/clang has been imported which may account 
> to some of the slowdown.
> 

Is the update of clang the only change? If so, maybe that's it.
Surprising nonetheless. The system is a Pi3, unaltered for about
six months. During buildworld it often shows near zero cpu activity,
seemingly while installing files. I wondered if maybe something had
changed in the filesystem drivers or scheduler. The machine uses a
goodly amount of swap, but only for two brief intervals during
buildworld. That slowdown is normal, expected and relatively brief.

The pattern is to run make cleandir twice, then remove /usr/obj, then
make -j4 buildworld with whatever settings are default. I belive those
steps are somewhat redundant but do so for consistency with past practice.

It might be worth noting that /boot/loader.conf contains one special line:
vm.pageout_oom_seq="2048" to give the system enough patience to use the 4 
GB of available swap. None of this is new, however, and the periods of high 
idle time don't always conincide with high swap use.


Thanks for reading!

bob prohaska