HEADS UP! Kernel debugging disabled in RELENG_5 [Fwd: cvscommit: src/sys/sparc64/conf GENERIC]

Scott Long scottl at samsco.org
Tue Sep 7 17:36:01 PDT 2004

Brian Fundakowski Feldman wrote:
> On Tue, Sep 07, 2004 at 05:55:29PM -0600, Scott Long wrote:
>>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).

I've measured an approx 5% overhead in using invariants.  It is a well
documented option and those who are concerned about it can turn it back
on locally, just like in 4.x and 3.x etc etc.  As for DDB, it does have
it's warts but I've also been using it successfully recently, even with
breakpoints.  The only problem I've had is with a breakpoint firing
while DDB is exiting.


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