Message-ID: <59885C5E3098D511AD690002A5072D3C02AB7DF0@orsmsx111.jf.intel.com>
From: "Grover, Andrew" <andrew.grover@intel.com>
To: "'Andrew Theurer'" <habanero@us.ibm.com>, linux-kernel@vger.kernel.org
Subject: RE: Hyperthreading and physical/logical CPU identification
Date: Mon, 29 Apr 2002 12:40:42 -0700
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Sender: linux-kernel-owner@vger.kernel.org

> From: Andrew Theurer [mailto:habanero@us.ibm.com] 
> I would like to know if there is any way to confirm that I have 
> hyperthreading enabled, and my P4 CPUs are hyperthreaded.  
> Actually, from 
> something like /proc/cpuinfo, I'd like to figure out if I am 
> seeing 2/4 
> physical/logical processors, as a result from hyperthreading, or 4/4 
> physical/logical processors with no hyperthreading.  I know, 
> "If it's double 
> the number of physical processors, well you have 
> hyperthreading enabled."  
> The problem is, I have 4 physical processors, but kernel.org 
> kernels so far 
> do not recognize all of them.  2.4.18 will find 3, while 
> 2.5.11 will find 
> only 2 (BIOS hyperthreading support off, no acpismp=force).  
> However, on 
> 2.5.11, if I enable hyperthreading (thru BIOS and 
> acpismp=force, I see 4 
> processors.  
> 
> I would very much like to believe that in this configuration, 
> I am only 
> running on 2 physical, 4 logical processors, but I am getting a 31% 
> improvement (netbench) when hyperthreading is enabled.  Thats 
> why I want to 
> confirm I am really only using 2 physical, 4 logical 
> processors.  Is there 
> any way I can do this? (dmesg? /proc/cpuinfo?)

Well the two alternatives are, either A) turning on hyperthreading enabled
the two virtual processors or B) turning on hyperthreading somehow enabled
the other two processors, right?

I would think B would be highly unlikely.

Anyone else who actually has HT hardware care to comment? ;-)

Regards -- Andy
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