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Re: unexpected IO-APIC, 2.4.36 SMP, AMD dual core Opteron



Tuynman, William (JSC-DT/USA)[USA] wrote:
Thanks for the response.
For now, we are stuck with running a 2.4 kernel. We have applications
that will not run under a 2.6 kernel with a current Red Hat software
release. Yes we did try but figured it was easier and safer to run 2.4
on the new hardware.
We do plan to upgrade but it's going to take a year or 2 because of the
amount of code and the need to purchase new versions of COTS products,
testing and all that. In the meantime, these new machines need to run
the same applications as the other machines that we have.

If you have the luxury of a serious test, I believe that CPU has the hardware support needed to run a 2.4 virtual machine under xen or kvm, and you might be able to postpone the upgrade of applications somewhat longer.

I tried 2.4.36 because it was just released and improvements have been
incorporated from time to time.

Clearly worth trying.

NOTE: The kernel appears to run correctly in spite of the IO-APIC
message. So, it appears that the message is more of a warning than an
error? Possibly there is some degradation that I'm not aware of but the
system doesn't need to do a lot of IO.

I believe you're right, but there are some boot options to control lapic, apic, io-apic, apci, etc. Some selective boot options might get rid of the warnings. I can't remember just what were 2.4, I think a lot of the ones I'm remembering ar 2.6, but there still may be some joy in trying what you can.

The IO-APIC message does not occur with a 2.6 kernel. I have one of the
machines running with 2.6.22.13 So, it  appears to be 2.4 related. I
assume that's why you suggested the "live CD"

Yes, to allow testing without any chance of messing up your existing setup. It's a safe way to find out how it's going to work.

For this build I specified the Athlon processor, which is the same as I
specified for the 2.6 kernel. I'll try  the Opteron and possibly a more
generic type to see what happens.

Let me know how you make out, bet you guys are busy right now. ;-)

Bill

-----Original Message----- From: Bill Davidsen [mailto:davidsen@xxxxxxx] Sent: Wednesday, February 06, 2008 6:07 PM
To: Tuynman, William (JSC-DT/USA)[USA]
Cc: linux-smp@xxxxxxxxxxxxxxx
Subject: Re: unexpected IO-APIC, 2.4.36 SMP, AMD dual core Opteron

Tuynman, William (JSC-DT/USA)[USA] wrote:
Hello,
	I have been getting this "An unexpected IO-APIC was found"
message. In checking, it occurs on 2.4.34 also.
	The kernel was compiled for 32 bit execution and is running on
an AMD dual core Opteron. The machine is an HP Proliant, DL 585.
I'm attaching, as text, a portion of the messages file which contains
all of the boot information.
I would be happy to assist with providing additional information that
would be helpful to you.
The first question I have is, why are you running a 2.4 kernel on a
modern CPU? I suspect the SMP logic in 2.4.26 is a decade older than the
hardware. SMP was pretty unusual then, multi-core was just not an end
user feature. I don't doubt that the IO-APIC may have unsupported
features.

Might I suggest that you boot off a recent "live CD" like Fedora or
Puppy Linux, just to see if you still see a problem. If not, you will
have more information to evaluate your next step.


--
Bill Davidsen <davidsen@xxxxxxx>
  "Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark

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--
Bill Davidsen <davidsen@xxxxxxx>
 "Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark

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