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?
Date: Fri, 25 Oct 2002 13:38:57 +0100 [thread overview]
Message-ID: <20021025123857.GA1091@suse.de> (raw)
In-Reply-To: <20021024230229.GA1841@vmware.com>
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
next prev parent reply other threads:[~2002-10-25 12:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-24 23:02 chrisl
2002-10-25 0:47 ` Andrew Walrond
2002-10-25 8:26 ` Gianni Tedesco
2002-10-25 8:27 ` Martin J. Bligh
2002-10-25 18:20 ` chrisl
2002-10-25 18:35 ` David T Hollis
2002-10-25 18:52 ` Martin J. Bligh
2002-10-25 12:38 ` Dave Jones [this message]
2002-10-25 19:07 ` chrisl
2002-10-25 18:54 Nakajima, Jun
2002-10-25 19:12 ` chrisl
2002-10-25 19:05 Nakajima, Jun
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