[nycbug-talk] make -jN performance was: Re: talk Digest, Vol 14, Issue 9
Wed Jan 19 16:24:17 EST 2005
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.
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.
"Certainly the game is rigged. Don't let that stop you; if you don't
bet, you can't win."
-- Robert Heinlein
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