Re: buildworld times

From: Robert Watson (rwatson_at_freebsd.org)
Date: 02/29/04

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    Date: Sat, 28 Feb 2004 21:03:58 -0500 (EST)
To: Vincent Poy <vince@oahu.WURLDLINK.NET>

    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@fledge.watson.org Senior Research Scientist, McAfee Research

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