* Re: 2.4.19 kernel incorrectly reports # CPUs
2002-09-11 15:53 2.4.19 kernel incorrectly reports # CPUs Watson, Randy E
@ 2002-09-11 13:00 ` Arnaldo Carvalho de Melo
2002-09-11 15:56 ` Randy.Dunlap
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Arnaldo Carvalho de Melo @ 2002-09-11 13:00 UTC (permalink / raw)
To: Watson, Randy E; +Cc: 'linux-smp@vger.kernel.org'
Em Wed, Sep 11, 2002 at 08:53:32AM -0700, Watson, Randy E escreveu:
> I have built the 2.4.19 kernel for a dual processor Xeon system with a
> SuperMicro P4DC6 mainboard.The kernel incorrectly finds four CPUs
> instead of the two it has. Using "top" shows four active CPUs and cpuinfo
> also shows four CPUs. I have built/run a number of other kernels (2.4.18,
> 2.5.33)
> recently on this system and they don't exhibit this problem.
>
> What may be causing this?
Hiperthreading support? Gee, you got two new CPUs! 8)
- Arnaldo
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: 2.4.19 kernel incorrectly reports # CPUs
2002-09-11 15:53 2.4.19 kernel incorrectly reports # CPUs Watson, Randy E
2002-09-11 13:00 ` Arnaldo Carvalho de Melo
@ 2002-09-11 15:56 ` Randy.Dunlap
2002-09-11 15:56 ` Mathieu Chouquet-Stringer
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Randy.Dunlap @ 2002-09-11 15:56 UTC (permalink / raw)
To: Watson, Randy E; +Cc: 'linux-smp@vger.kernel.org'
On Wed, 11 Sep 2002, Watson, Randy E wrote:
| I have built the 2.4.19 kernel for a dual processor Xeon system with a
| SuperMicro P4DC6 mainboard.The kernel incorrectly finds four CPUs
| instead of the two it has. Using "top" shows four active CPUs and cpuinfo
| also shows four CPUs. I have built/run a number of other kernels (2.4.18,
| 2.5.33)
| recently on this system and they don't exhibit this problem.
|
| What may be causing this?
| -
"Hyperthreading"? support added in 2.4.19.
2 logical CPUs per chip in Intel P4 Xeons.
However, I would expect 2.5.33 to show the same symptom.
If it's a problem, you can disable it with "noht" on the
kernel load/command line.
If there's some doubt about this, you could post your
/proc/cpuinfo file and kernel boot log.
--
~Randy
"Linux is not a research project. Never was, never will be."
-- Linus, 2002-09-02
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: 2.4.19 kernel incorrectly reports # CPUs
2002-09-11 15:53 2.4.19 kernel incorrectly reports # CPUs Watson, Randy E
2002-09-11 13:00 ` Arnaldo Carvalho de Melo
2002-09-11 15:56 ` Randy.Dunlap
@ 2002-09-11 15:56 ` Mathieu Chouquet-Stringer
2002-09-11 16:02 ` Eff Norwood
2002-09-11 16:25 ` Robert M. Hyatt
4 siblings, 0 replies; 6+ messages in thread
From: Mathieu Chouquet-Stringer @ 2002-09-11 15:56 UTC (permalink / raw)
To: "Watson, Randy E"; +Cc: linux-smp
randy.e.watson@boeing.com ("Watson, Randy E") writes:
> I have built the 2.4.19 kernel for a dual processor Xeon system with a
> SuperMicro P4DC6 mainboard.The kernel incorrectly finds four CPUs
> instead of the two it has. Using "top" shows four active CPUs and cpuinfo
> also shows four CPUs. I have built/run a number of other kernels (2.4.18,
> 2.5.33)
> recently on this system and they don't exhibit this problem.
>
> What may be causing this?
Hi Randy,
the cause of this is HT (HyperThreading) thus your dual Xeon (with HT
enabled) looks like a quad CPU.
This is expected behaviour...
--
Mathieu Chouquet-Stringer E-Mail : mathieu@newview.com
It is exactly because a man cannot do a thing that he is a
proper judge of it.
-- Oscar Wilde
^ permalink raw reply [flat|nested] 6+ messages in thread* RE: 2.4.19 kernel incorrectly reports # CPUs
2002-09-11 15:53 2.4.19 kernel incorrectly reports # CPUs Watson, Randy E
` (2 preceding siblings ...)
2002-09-11 15:56 ` Mathieu Chouquet-Stringer
@ 2002-09-11 16:02 ` Eff Norwood
2002-09-11 16:25 ` Robert M. Hyatt
4 siblings, 0 replies; 6+ messages in thread
From: Eff Norwood @ 2002-09-11 16:02 UTC (permalink / raw)
To: Watson, Randy E, linux-smp
> I have built the 2.4.19 kernel for a dual processor Xeon system with a
> SuperMicro P4DC6 mainboard.The kernel incorrectly finds four CPUs
> instead of the two it has. Using "top" shows four active CPUs and cpuinfo
> also shows four CPUs. I have built/run a number of other kernels (2.4.18,
> 2.5.33)
> recently on this system and they don't exhibit this problem.
>
> What may be causing this?
The fact that hyperthreading is enabled in the BIOS causes each Xeon to act
as 2 processors, thus Linux correctly identifies 4 processors.
Best,
Eff Norwood
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: 2.4.19 kernel incorrectly reports # CPUs
2002-09-11 15:53 2.4.19 kernel incorrectly reports # CPUs Watson, Randy E
` (3 preceding siblings ...)
2002-09-11 16:02 ` Eff Norwood
@ 2002-09-11 16:25 ` Robert M. Hyatt
4 siblings, 0 replies; 6+ messages in thread
From: Robert M. Hyatt @ 2002-09-11 16:25 UTC (permalink / raw)
To: Watson, Randy E; +Cc: 'linux-smp@vger.kernel.org'
hyper-threading makes a single cpu look like two.
On Wed, 11 Sep 2002,
Watson, Randy E wrote:
> I have built the 2.4.19 kernel for a dual processor Xeon system with a
> SuperMicro P4DC6 mainboard.The kernel incorrectly finds four CPUs
> instead of the two it has. Using "top" shows four active CPUs and cpuinfo
> also shows four CPUs. I have built/run a number of other kernels (2.4.18,
> 2.5.33)
> recently on this system and they don't exhibit this problem.
>
> What may be causing this?
> -
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>
--
Robert Hyatt Computer and Information Sciences
hyatt@cis.uab.edu University of Alabama at Birmingham
(205) 934-2213 115A Campbell Hall, UAB Station
(205) 934-5473 FAX Birmingham, AL 35294-1170
^ permalink raw reply [flat|nested] 6+ messages in thread