Kernel Panic booting cdrom
michael at ellerman.id.au
Mon Apr 23 12:10:22 EST 2007
On Fri, 2007-04-20 at 14:05 -0700, David Huffman wrote:
> I think I determined why I received a kernel panic and the numa=off
> argument fixed the problem. When we boot from cdrom we specify maxcpus=1
> as a kernel argument. A system with numa enabled fails. I plan on
> adding numa=off whenever I use maxcpus=1, but I wonder if you could
> answer a question for me.
> I originally was told that in the case where I am booting a basic system
> into an initrd instead of in normal mode, I should use maxcpus=1 because
> there may be power and cooling daemons that are not running and try to
> limit the system resources by limiting the number of cpus. Does this
> sound right? I can successfully boot a cdrom without the maxcpus flag on
> an SMP system but maybe it is typically not a good idea?
> I can prevent the kernel panics by removing maxcpus=1 and not adding
> numa=off. I am a little more informed about numa (now), but I am fuzzy
> as to all the implications with allowing more cpus for cdrom install
> media. The maxcpus=1 argument was something we added to our install boot
> media years ago and few here remember why it was such a great idea. The
> power/resource management was the only thing we could come up with.
maxcpus=x is poorly tested, I would definitely NOT recommend it.
I don't think there's any issue with power etc. With maxcpus=1 all the
other CPUs are still running, they're just not used by the kernel - in
fact a cursory glance suggests they will do less power saving in that
situation than when they're in use but idle.
OzLabs, IBM Australia Development Lab
phone: +61 2 6212 1183 (tie line 70 21183)
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we borrow it from our children. - S.M.A.R.T Person
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