[nycbug-talk] make -jN performance was: Re: talk Digest, Vol 14, Issue 9

[Tillman Hodgson]

On Tue, Jan 18, 2005 at 05:59:15PM -0500, Pete Wright wrote:
> Hey bob all,
> 	so instead of relying on blind faith I ran some tests to see the truth
> in the make -jN statements in the FreeBSD handbook.  While I agree with what 
> bob stated regarding the "-j" flag I thought that maybe there was something in
> the makeworld process that got around these issues.  Well I hacked up a small
> shell script to test this out and the findings were not what I expected (and 
> frankly not what I remember experiencing in the past).  The make times flattened
> out after make -j2 buildworld on an SMP system running 5.3.  I've posted a pretty detailed
> post to freebsd-stable@ and hope to get some feedback.  I'll keep you all posted
> here as well if you all are interested.

About a year ago I did some tests as well.

http://lists.freebsd.org/pipermail/freebsd-questions/2004-January/032105.html

I posted this to the FreeBSD questions mailing list though it didn't
generate much discussion. After testing for myself and seeing these
results, I quit using -j# with make on single CPU boxes.

Combined with your results, it looks like one job per CPU is the best
that the build infrastructure can do.

-T


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