[Fedora-xen] Newbie question regarding Xen traps

[Alex Tomic]

Hey Rik (reply to list)

I forgot to thank you for this response. I had planned to buy a serial cable
if I had any more instability after upgrading. 

After doing the full-blown yum update for my stock FC5_x86_64 boxes (to
kernel 2.6.17-1.2157_FC5xen0 and Xen-3.0.2-3), I have had no such crashes
after 13 days. I really wish I had the stack traces so you could at least
identify a fixed bug, but I don't have the luxury of being able to go back
to an old code release and reproduce the problem, at least not now. 

If anyone on this list experiences instability when stressing mysql on a
x86_64 VM, especially with a stack that has mask_IO_APIC_irq or
mask_and_ack_level_ioapic_irq in it (not sure exactly what these do), I
would suggest doing an upgrade to the latest Xen on Dom0; I did not upgrade
the guest OSes, they are still on the stock FC5 guest kernel
(2.6.15-1.2054_FC5xenU) 

-Alex
---------------------------------------------
Alex Tomic
Database Administrator, Gifts.com
8833 Sunset Blvd, 3rd Floor
West Hollywood, CA 90069
Phone: (310) 360-4332

-----Original Message-----
From: Rik van Riel [mailto:riel at redhat.com] 
Sent: Tuesday, August 08, 2006 4:20 PM
To: Alex Tomic
Cc: fedora-xen at redhat.com
Subject: Re: [Fedora-xen] Newbie question regarding Xen traps

Alex Tomic wrote:

> My question is, how do I retain the trap output that is printed to the 
> console when the machine dies? 

Serial console.

The easiest thing is to buy two serial cables and have both
systems act as serial console server for the other, using
the excellent ttywatch program from Fedora Extras.

If one crashes, the other will log all the crash output.

Don't forget to also configure the hypervisor for serial
console output.  Your grub.conf will look like this:

title Fedora Core (2.6.17-1.2488.fc6xen)
         root (hd0,0)
         kernel /xen.gz-2.6.17-1.2488.fc6 com1=38400,8n1
         module /vmlinuz-2.6.17-1.2488.fc6xen ro root=LABEL=/ 
console=ttyS0,38400 mem=2000M panic=180 debug 3
         module /initrd-2.6.17-1.2488.fc6xen.img


When you get a backtrace, please file a bugzilla and feel
free to add me to the CC: list.  I have a very strong
personal interest in fixing x86-64 Xen bugs, since I want
to get rid of a (noisy, warm) server at home and move that
workload into a virtual machine on my new desktop system :)

-- 
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan