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Date: Tue, 21 Oct 2008 17:19:40 -0500
From: Nathan Whitehorn <nwhitehorn@freebsd.org>
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To: Peter Grehan <grehan@freebsd.org>
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Cc: freebsd-ppc@freebsd.org
Subject: Re: graphics on G4
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Peter Grehan wrote:
> Hi Justin,
>
>   
>>>  The framebuffer uses a large chunk of kernel VM when mmap'd.
>>> Are you able to dump some vm stats while doing this e.g.
>>> sysctl vm.kvm_free ?
>>>       
>
>  I shouldn't hit send before the morning coffee :( mmap'ing
> uses process VM, not kernel, except for the extra alloc's
> needed for this but these should all come from the non-KVA UMA
> small malloc area.
>   
One thing that worries me about our PMAP layer could cause this. This 
machine has a lot of RAM. What happens if we have physical or device 
memory in the same range as kmem VAs? It seems like trying to modify it 
through the BAT map (as zero/copy page, /dev/mem and friends do) will 
overwrite random bits of KVA instead...
-Nathan