Re: RPi 4 build time

On 2021-May-22, at 18:36, Mark Millard via freebsd-arm <freebsd-arm at freebsd.org> wrote:

> On 2021-May-22, at 18:23, tech-lists <tech-lists at zyxst.net> wrote:
> 
>> On Sat, May 22, 2021 at 04:51:31PM -0700, Mark Millard via freebsd-arm wrote:
>> 
>>> In general these figures are approximations of the low
>>> bound on a buildworld that is a (near) no-op but is
>>> not frequently approached in my normal activity. But
>>> it is rare for me to update the source tree again
>>> and rebuild after only a few source commits after
>>> what was originally rebuilt. For such, sub-half hour
>>> rebuilds can certainly occur via META_MODE use.
>>> 
>>> The context happened to be the ZFS based one in all
>>> cases. Still no ccache use.
>> 
>> That's wild. I have to look at meta mode. 
>> My use case though mostly involves building/updating ports with
>> poudriere, and I'm happy it can use ccache.
>> 
>> Am I right in thinking meta mode is a buildworld/kernel thing only? I've
>> only heard of it; I know nothing about it.
> 
> Yep: buildworld buildkernel only.
> 
> META_MODE does not help for after a "rm -rf /usr/obj/*"
> sort of clean-out. It just attempts to avoid rebuilding
> materials already present that are sufficient. (It still
> builds more than is strictly necessary: Some of the
> dependency tracking tracks things that do not actually
> imply needing a file rebuild. This is why installworld
> to the live system ends up leading to a larger rebuild
> later.)
> 

I should have also mentioned the other side of
META_MODE: It is there to also be sure to rebuild
things that do need to be rebuilt. Its rebuilding
more than necessary generally avoids ending up with
insufficient/inaccurate rebuilds. Between ending
up with false positives vs. false negatives, it
has a definite bias.


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)