Re: 2.4.20-rc2 strange L1 cache values

From: Steffen Persvold (sp@scali.com)
Date: Wed Nov 20 2002 - 13:48:27 EST


On Wed, 20 Nov 2002, Dave Jones wrote:

> On Wed, Nov 20, 2002 at 07:05:06PM +0100, Margit Schubert-While wrote:
> > Any ideas anybody ?
> > <6>CPU: L1 I cache: 0K, L1 D cache: 8K
> > <6>CPU: L2 cache: 512K
> > <6>Intel machine check architecture supported.
> > <6>Intel machine check reporting enabled on CPU#0.
> > <7>CPU: After generic, caps: 3febfbff 00000000 00000000 00000000
> > <7>CPU: Common caps: 3febfbff 00000000 00000000 00000000
> > <4>CPU: Intel(R) Pentium(R) 4 CPU 2.40GHz stepping 04
>
> P4 Trace cache isn't recognised.
> Apply ftp://ftp.kernel.org/pub/linux/kernel/people/davej/patches/2.4/2.4.20/descriptors.diff
>

Yep that works (I have two Xeon boxes with the same issue) :

(2.4.20-rc2 with descriptors.diff)
CPU: Trace cache: 12K uops, L1 D cache: 8K
CPU: L2 cache: 512K
CPU: Physical Processor ID: 0
Intel machine check reporting enabled on CPU#0.
CPU: After generic, caps: 3febfbff 00000000 00000000 00000000
CPU: Common caps: 3febfbff 00000000 00000000 00000000
CPU0: Intel(R) XEON(TM) CPU 1.80GHz stepping 04

But why does this P4 Trace cache report as L1 I cache on 2.4.18 ?

(2.4.18)
CPU: Before vendor init, caps: 3febfbff 00000000 00000000, vendor = 0
CPU: L1 I cache: 12K, L1 D cache: 8K
CPU: L2 cache: 512K
CPU: Physical Processor ID: 0
CPU: After vendor init, caps: 3febfbff 00000000 00000000 00000000
Intel machine check reporting enabled on CPU#0.
CPU: After generic, caps: 3febfbff 00000000 00000000 00000000
CPU: Common caps: 3febfbff 00000000 00000000 00000000
CPU0: Intel(R) XEON(TM) CPU 1.80GHz stepping 04

Does this have any implications on the 2.4.18 performance (or the
2.4.20-rc2 performance without the descriptors.diff) ?

Regards,

-- 
  Steffen Persvold   |       Scali AS      
 mailto:sp@scali.com |  http://www.scali.com
Tel: (+47) 2262 8950 |   Olaf Helsets vei 6
Fax: (+47) 2262 8951 |   N0621 Oslo, NORWAY

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