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Date: Sun, 28 Jun 2009 20:14:24 -0400
From: Nathanael Hoyle <nhoyle@hoyletech.com>
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To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: large pages (amd64)
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Wojciech Puchar wrote:
> i enabled
> vm.pmap.pg_ps_enabled: 1
>
>
> could you please explain what exactly this values means?
> because i don't understand why promotions-demotions!=mappings
>
> vm.pmap.pde.promotions: 2703
> vm.pmap.pde.p_failures: 6290
> vm.pmap.pde.mappings: 610
> vm.pmap.pde.demotions: 289
>
>
>
>
> other question - tried enabling it on my i386 laptop (256 megs ram), 
> always mappings==0, while promitions>demotions>0.
>
> certainly there are apps that could be put on big pages, gimp editing 
> 40MB bitmap for example

Just to be clear, since you say i386 (I presume you mean architecture), 
I believe the Physical Address Extensions which allowed 2MB Page Size 
bit to be set was introduced with Pentium Pro. Processors prior to this 
were limited to standard 4KB pages.

-Nathanael