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Date: Wed, 5 Mar 2003 12:58:49 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Gerrit Huizenga <gh@us.ibm.com>
Cc: "Reed, Timothy A" <timothy.a.reed@lmco.com>,
       "Linux Kernel ML (E-mail)" <linux-kernel@vger.kernel.org>
Subject: Re: High Mem Options
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On Wed, 05 Mar 2003 04:26:54 PST, William Lee Irwin III wrote:
>> Yes, the additional level of pagetables slows things down quite a bit.

On Wed, Mar 05, 2003 at 12:31:03PM -0800, Gerrit Huizenga wrote:
> Bill, do you hvae measures for this?  I seem to remember PTX's impact
> of PAE36 as being about 3-5% depending on workload.  Janet did one test
> sometime back with DB2 that showed a net of no difference on TPC-H (PAE
> slows things down, less memory pressure speeds things up) but Badari
> just repeated with 2.5.62 or 2.5.63 and saw a larger degradation.
> I'm wondering if some hardware is not getting correctly configured at
> boot with with respect to MTRR's, perhaps...  I really wouldn't expect
> a 10% impact from PAE and I don't have any consistent Linux measurements
> to validate or invalidate that much impact.

Unfortunately the number of ca. 10% I got from you. I think badari's
done some $BENCHMARK_THAT_CANNOT_BE_NAMED things recently that were
consistent with the handwavy estimate but AIUI they were not intended
to measure the effect etc. etc.


-- wli
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