make -j$n buildworld : use of -j investigated

[Rob]

Laurence Sanford wrote:
> Rob wrote:
> 
>> ----------------------------------------
>>
>> With these simple tests, I come to the conclusion that
>> "make -j$n buildworld" is best with n = number of CPUs.
>> Does that make sense?
>>
>> Rob.
> 
> This is what I've been telling people and using myself for years. 
> However, I've been shot down on this several times, so I just leave 
> everyone alone and let them do their own thing. You and I will be 
> getting it done a little faster though.

Not really faster, but higher values do not make a difference,
well, as long as the extra processes do not force the use of
swap. Intensified swapping because of a high -j value slows
down the build considerably.

I don't understand why this is reason for debate. My test has
obvious results on various of my PCs, and was very quickly done:
I wrote a script with a loop that built the world again and
again, doing a 'touch' to a file immediately before and after
the build. Got all my data within a day or so.

Rob.