Messages in this thread | | | Date | Wed, 13 Feb 2002 12:42:03 +0100 (CET) | From | Martin Wilck <> | Subject | SMT, again (was: Re: [PATCH]: Fix MTRR handling on HT CPUs) |
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I just found out that Intel specifies that on SMT-enabled ("Jackson") systems the BIOS MP tables list only the physical CPUs. Logical CPUs will only be available through the ACPI tables.
See http://www.intel.com/technology/hyperthread/platform_nexgen/, in particular sld014.htm, sld021.htm.
This will basically obsolete the patch we were discussing, if BIOS manufacturers comply to that spec, because linux will only see the 2 physical CPUs. (The problem we discovered was caused by our BIOS not complying to the spec).
Of course, it would also mean that Linux will only run on ~70% of the CPU power that Win2k/XP systems will have available on such systems.
All my attempts to get ACPI running on our SMT-enabled system have failed so far (I'm working on a bug report on that for linux-acpi).
A possible workaround would be the "processor affinity algorithm" sketched in sld021.htm, but it may be unreliable because it overrides BIOS settings (BIOS-diabled CPUs) that are available only through ACPI.
Sorry to bother if you knew this already.
Martin
-- Martin Wilck Phone: +49 5251 8 15113 Fujitsu Siemens Computers Fax: +49 5251 8 20409 Heinz-Nixdorf-Ring 1 mailto:Martin.Wilck@Fujitsu-Siemens.com D-33106 Paderborn http://www.fujitsu-siemens.com/primergy
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