From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: Kernel Panic booting cdrom From: Michael Ellerman To: David Huffman In-Reply-To: <46292B07.3030907@storix.com> References: <46202254.1090606@storix.com> <20070414044529.GE6062@localdomain> <4623F574.1030804@storix.com> <20070417054537.GF6062@localdomain> <46292B07.3030907@storix.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-i0uLWTZ4rvsTLc+Bt9Hf" Date: Mon, 23 Apr 2007 12:10:22 +1000 Message-Id: <1177294222.3889.9.camel@concordia.ozlabs.ibm.com> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, Nathan Lynch Reply-To: michael@ellerman.id.au List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-i0uLWTZ4rvsTLc+Bt9Hf Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Fri, 2007-04-20 at 14:05 -0700, David Huffman wrote: > Nathan, >=20 > I think I determined why I received a kernel panic and the numa=3Doff=20 > argument fixed the problem. When we boot from cdrom we specify maxcpus=3D= 1=20 > as a kernel argument. A system with numa enabled fails. I plan on=20 > adding numa=3Doff whenever I use maxcpus=3D1, but I wonder if you could=20 > answer a question for me. >=20 > I originally was told that in the case where I am booting a basic system=20 > into an initrd instead of in normal mode, I should use maxcpus=3D1 becaus= e=20 > there may be power and cooling daemons that are not running and try to=20 > limit the system resources by limiting the number of cpus. Does this=20 > sound right? I can successfully boot a cdrom without the maxcpus flag on=20 > an SMP system but maybe it is typically not a good idea? >=20 > I can prevent the kernel panics by removing maxcpus=3D1 and not adding=20 > numa=3Doff. I am a little more informed about numa (now), but I am fuzzy=20 > as to all the implications with allowing more cpus for cdrom install=20 > media. The maxcpus=3D1 argument was something we added to our install boo= t=20 > media years ago and few here remember why it was such a great idea. The=20 > power/resource management was the only thing we could come up with. maxcpus=3Dx is poorly tested, I would definitely NOT recommend it. I don't think there's any issue with power etc. With maxcpus=3D1 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. cheers --=20 Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person --=-i0uLWTZ4rvsTLc+Bt9Hf Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBGLBWOdSjSd0sB4dIRAirSAJ48cgjD8PFGognQg4qf6c1BC7a2VQCeN6jg kZfLY28R5ZbcW0ebYQXYqww= =kJL5 -----END PGP SIGNATURE----- --=-i0uLWTZ4rvsTLc+Bt9Hf--