Date: Sat, 25 May 2002 19:41:17 -0700 From: Peter Wemm <peter@wemm.org> To: Paul Saab <ps@mu.org> Cc: John Polstra <jdp@polstra.com>, smp@FreeBSD.ORG, bright@mu.org Subject: Re: hyperthreading: myth or legend? (was Re: hyperthreading? (was Re: question)) Message-ID: <20020526024117.1F07A3808@overcee.wemm.org> In-Reply-To: <20020526012953.GA51786@elvis.mu.org>
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Paul Saab wrote: > John Polstra (jdp@polstra.com) wrote: > > FWIW, my experience has been different. Yesterday I tried both the > > latest -current and 4.5-RELEASE on a Dell 2650, and both kernels > > failed to probe the extra processor cores. My colleagues who have > > been working with the system told me that XP does detect them. Maybe > > XP stands for Xtra Processors? ;-) > > > > Under FreeBSD I ran the "mptable" command, and it lists only one CPU > > per physical processor module. So at least for this particular BIOS, > > the kernel would have to Just Know that each processor has 2 cores in > > order to utilize them. > > You have to start the other cores. Peter has more info on how to do this. There seems to be two ways this is done. Some systems list the extra virtual cores in the mptable, others do not. Intel documents it such that if you want to get dependable core discovery, you need to use the ACPI processor info. The first version of the intel docs I read explicitly said that the logical cores were *not* to be listed in mptable. It would seem that this is rather inconsistent already. You can also grovel around in the cpuid results as well and you can find additional logical cores on the current cpu that way too. Cheers, -Peter -- Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com "All of this is for nothing if we don't go to the stars" - JMS/B5 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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