Date: Tue, 11 Mar 2003 15:36:57 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: Richard Nyberg <rnyberg@it.su.se> Cc: freebsd-smp@FreeBSD.org Subject: Re: hyperthreading randomness Message-ID: <XFMail.20030311153657.jhb@FreeBSD.org> In-Reply-To: <20030311203003.GA216@murmeldjur.it.su.se>
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On 11-Mar-2003 Richard Nyberg wrote: > On Mon, Mar 10, 2003 at 01:00:13PM -0500, John Baldwin wrote: >> >> On 08-Mar-2003 Richard Nyberg wrote: >> > I have a Dell Precision 450 with 2 xeon CPU:s. >> > The weird thing is that it randomly boots up >> > with either 2 or 4 CPUs on the same 4-STABLE kernel. >> > 2 more often than 4. It seems a bit unpredictable :( >> >> Hmm, I have no idea about that one. Hmm, it seems to be a >> "feature" of the BIOS perhaps. It seems that it may be listing >> the second CPU with an APIC ID of 3 (it's second core) instead >> of 2 (it's first core) in which case the HTT code sees that >> something is not right and doesn't start up any extra processors. >> > This patch works for me ;) It allows the physical CPUs APIC ID to > be either the lowest (as is currently assumed) or the highest > number in the range of APIC IDs for the logical cores. I'm not sure it's entirely safe since it doesn't verify that you are at the top of a boundary when it looks downwards. Really though, the current stuff is more of a quick hack to get it mostly working for now. When the ACPI stuff gets done it won't really matter anymore. I'd like to keep the current hack very conservative since I'm making assumptions that I am not completely sure I am allowed to make and I'd like to keep the number and scope of such assumptions as small as possible. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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