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Date: Fri, 6 Dec 2002 16:21:33 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Andrew Morton <akpm@digeo.com>
Cc: Andrea Arcangeli <andrea@suse.de>, Norman Gaywood <norm@turing.une.edu.au>,
       linux-kernel@vger.kernel.org
Subject: Re: Maybe a VM bug in 2.4.18-18 from RH 8.0?
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> William Lee Irwin III wrote:
> > 
> > ...
> > A 16KB or 64KB kernel allocation unit would then annihilate
> 
On Fri, Dec 06, 2002 at 04:01:24PM -0800, Andrew Morton wrote:
> You want to be careful about this:
> 	CPU: L1 I cache: 16K, L1 D cache: 16K
> Because instantiating a 16k page into user pagetables in
> one hit means that it must all be zeroed.  With these large
> pagesizes that means that the application is likely to get
> 100% L1 misses against the new page, whereas it currently
> gets 100% hits.

16K is reasonable; after that one might as well go all the way.
About the only way to cope is amortizing it by cacheing zeroed pages,
and that has other downsides.


Bill
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