Date: Wed, 8 Sep 2004 18:32:46 +0000 From: Kris Kennaway <kris@FreeBSD.org> To: Brian Fundakowski Feldman <green@FreeBSD.org> Cc: freebsd-current@FreeBSD.org Subject: Re: HEADS UP! Kernel debugging disabled in RELENG_5 [Fwd: cvs commit: src/sys/i386/conf GENERIC src/sys/pc98/conf GENERIC src/sys/sparc64/conf GENERIC] Message-ID: <20040908183246.GB66994@hub.freebsd.org> In-Reply-To: <20040908003141.GB928@green.homeunix.org> References: <413E4A71.9080400@samsco.org> <20040908003141.GB928@green.homeunix.org>
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On Tue, Sep 07, 2004 at 08:31:41PM -0400, Brian Fundakowski Feldman wrote:
> On Tue, Sep 07, 2004 at 05:55:29PM -0600, Scott Long wrote:
> > All,
> >
> > Since we are closing in on the 5.3 release, I've removed the kernel
> > debugging options from GENERIC in RELENG_5. They can of course be
> > re-enabled by adding the appropriate lines back in locally. However,
> > from now on when filing a kernel-related bug report, make sure to
> > enable WITNESS, INVARIANTS, and DDB/KDB to help determine the problem.
>
> It's not necessarily a good thing to disable INVARIANTS without verifying
> it has a huge cost in performance. It would be invaluable finding more
> bugs in production, and will likely be sorely missed. IT's also worth
> noting DDB/KDB is broken anyway in fairly large ways (on i386, at least,
> breakpoints don't work and even with the "fix" you get panics soon if
> you really do try to use them).
INVARIANTS does have quite a significant impact on performance.
5.3 + 4BSD + INVARIANTS
2205.39 real 3840.87 user 1583.64 sys
5.3 + 4BSD - INVARIANTS
1862.61 real 3752.97 user 1141.81 sys
That's the 'make world' time for the same source tree built under
different kernels.
Kris
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