FreeBSD and "make -j# buildworld" usability

Garance A Drosehn gad at FreeBSD.org
Mon Oct 16 22:33:39 UTC 2006


At 1:47 PM -0700 10/13/06, Kent Stewart wrote:
>On Friday 13 October 2006 07:31, Buki wrote:
>>  Hi,
>>
>>  I searched the archives and web a little but found many different
>>  opinions on stability/usability of using make -j# with buildworld
>>  (and buildkernel).
>>
>>  So I am asking if it is a good idea to use make -j on production
>>  boxes.
>>
>
>I tested buildworlds with different values for -j. On single processors,
>using a script that basically looked like
>
>time make -j? ...
>
>yielded fastest builds when I didn't specify a value for -j. On dual
>cpu's a value around -j8 yielded the fastest build.

You might want to repeat those performance tests.  The results will
change over time, as various system changes are made.  I used to see
results somewhat similar to yours, but the last time I checked I
seemed to get the best results from a dual-cpu system when using -j3 .

I believe that change in performance is due to some improvements
made to the `make' command itself, which solved some delays that
happened when -j was used.  However, I do not remember the details.

Performance comparisons like this will also depend on all the hardware
on the system, and not just the dual-CPU.  It can change depending on
much memory the machine has, for instance, or how fast the disks are
compared to the CPU's.

-- 
Garance Alistair Drosehn     =               drosehn at rpi.edu
Senior Systems Programmer               or   gad at FreeBSD.org
Rensselaer Polytechnic Institute;             Troy, NY;  USA


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