buildworld times

[Robert Watson]

On Sat, 28 Feb 2004, Vincent Poy wrote:

> On Sat, 28 Feb 2004, Robert Watson wrote:
> 
> > On Sat, 28 Feb 2004, Vincent Poy wrote:
> >
> > > > 2.5 hours seems a little high and would seem to indicate that you're
> > > > building world under a kernel that has all the debugging options enabled.
> > > > Could you make your kernel config available?
> > >
> > > 	Yeah, I recall that -CURRENT on a Mobile PII 366Mhz took the
> > > same amount of time so I would imagine the P4 would be faster since I
> > > remember PIII running at 800Mhz or so would take about 2 hours and the
> > > Athlon K7 at 1.2Ghz was about a little over an hour.  I'm using the
> > > standard GENERIC kernel and do have the debugging options enabled.
> >
> > Turning off the debugging options (especially WITNESS) can have a dramatic
> > effect on performance.  Give it a spin.  :-)
> 
> 	Besides the WITNESS and WITNESS_SKIPSPIN, do these have a big
> effect as well? 
> 
> options         DDB

No runtime cost, and useful if anything goes wrong :-).

> options         INVARIANTS

Small but non-zero cost.

> options         INVARIANT_SUPPORT

Space overhead, but other than memory overhead, no run-time cost.

> makeoptions DEBUG=-g

Makes your kernel build real slow, but won't change the kernel speed.

As you point out, debugging problems is a lot easier if you run with
INVARIANTS+WITNESS.  However, you may well see build times halve or more
by running without WITNESS.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Senior Research Scientist, McAfee Research