Messages in this thread |  | | | Date | Wed, 12 Oct 2005 15:19:27 -0700 | | From | "Siddha, Suresh B" <> | | Subject | Re: [discuss] [Patch 1/2] x86, x86_64: Intel HT, Multi core detection fixes |
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On Wed, Oct 12, 2005 at 11:49:04PM +0200, Andi Kleen wrote: > On Wednesday 12 October 2005 23:36, Siddha, Suresh B wrote: > > > Fields obtained through cpuid vector 0x1(ebx[16:23]) and > > vector 0x4(eax[14:25], eax[26:31]) indicate the maximum values and might not > > always be the same as what is available and what OS sees. So make sure > > "siblings" and "cpu cores" values in /proc/cpuinfo reflect the values as seen > > by OS instead of what cpuid instruction says. This will also fix the buggy BIOS > > cases (for example where cpuid on a single core cpu says there are "2" siblings, > > even when HT is disabled in the BIOS. > > http://bugzilla.kernel.org/show_bug.cgi?id=4359) > > I'm not too fond of this new booted_core variable. How about > you just put the true number of cores into x86_num_cores? > What should x86_num_cores be in your setup anyways if not > "booted cores"?
x86_num_cores (cpuid returned value) is required while right shifting the apicid to get the core-id and the package-id. booted_cores will indicate how many cores actually cameup. x86_num_cores can differ from "booted cores" in these scenarios a) x86_num_cores may not be '1' when multi-core is disabled in the BIOS b) "maxcpus=" kernel boot param c) logical hotplug
> Also I must admit the number of different variables to keep > track of multicore and siblingness starts to become mindboggling, > so I would recommend you add a fat overview comment somewhere > that describes their definition and relationship. Or better put > something into Documentation, it is probably as confusing for > user space /proc/cpuinfo consumer too.
I will send a new documentation patch.
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