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Date: Fri, 25 Oct 2002 13:38:57 +0100
From: Dave Jones <davej@codemonkey.org.uk>
To: chrisl@vmware.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: How to get number of physical CPU in linux from user space?
Message-ID: <20021025123857.GA1091@suse.de>
Mail-Followup-To: Dave Jones <davej@codemonkey.org.uk>, chrisl@vmware.com,
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On Thu, Oct 24, 2002 at 04:02:29PM -0700, chrisl@vmware.com wrote:
 > It seems that /proc/cpuinfo will return the number of logical CPU.
 > If the machine has Intel Hyper-Thread enabled, that number is bigger
 > than physical CPU number. Usually twice as big.
 > 
 > My question is, what is the reliable way for user space program
 > to detect the number of physical CPU in the current machine?
 > 
 > If in it is in the kernel, I can read from cpu_sibling_map[]
 > or phys_cpu_id[]. But it seems not easy read that from
 > user space.
 > 
 > Of course I can do "gdb /proc/kcore" to get them. But is there
 > any better way?

You can perform cpuid instructions in userspace to get the
number of siblings per physical package.

-- 
| Dave Jones.        http://www.codemonkey.org.uk
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