Re: pg_clog woes with 7.3.2 - Episode 2

cbbrowne@cbbrowne.com wrote:
> The "noapic" option seems a quasi-magical elixir for many sorts of
> ailments.
>
> I upgraded a box to 2.4.20 and discovered that my NIC was no longer
> properly recognized until I threw that option in.  Others in my
> office have /apparently/ the same hardware, and found they didn't
> need the option.
>
> As a "fix," it certainly seems to fall into the
> "snakeoil/superstition" category.  While it often seems to have a
> useful effect, I haven't located any actual explanations as to why
> it should be expected to work.

Well, when it comes to booting a computer, the placebo effect doesn't
really exist.  :-)

Normally I'd agree that "noapic" sounds and smells like snakeoil.  The
problem is that it has observable and repeatable effects on some
systems, and thus can't really be classified as snakeoil (much as one
might like to!).

Why should it be expected to work?  I don't know...possibly because
the APIC hardware is buggy (perhaps in very subtle ways) on some
systems?  Possibly because the APIC driver is subtlely incompatible
with certain APIC hardware?  Possibly because the APIC driver has
certain subtle bugs that only manifest themselves on certain
motherboards with certain peripheral devices?

Whatever the reason, the "noapic" option *does* work on certain
systems, so it unfortunately isn't something that can be dismissed as
mere superstition -- the computer isn't being asked its opinion of its
own health here, nor does it "know" that it should get "well" when
given different boot options.  No "placebo effect" involved, just
repeatable observation (that the observation isn't terribly repeatable
*across* systems does not diminish the validity of the observation).


-- 
Kevin Brown                          kevin@sysexperts.com