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Date: Mon, 26 Jul 2010 02:35:29 -0500
From: Alan Cox <alc@cs.rice.edu>
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To: "M. Warner Losh" <imp@bsdimp.com>
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Cc: mips@freebsd.org
Subject: Re: svn commit: r210460 - head/sys/mips/include
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M. Warner Losh wrote:
> In message: <AANLkTik+BV6u6fNVX8Ntb-G1yF=vEDh6VqB7Xcb5VtD-@mail.gmail.com>
>             "Jayachandran C." <c.jayachandran@gmail.com> writes:
> : On Sun, Jul 25, 2010 at 10:18 AM, Alan Cox <alc@cs.rice.edu> wrote:
> : > Warner Losh wrote:
> : >>
> : >> Author: imp
> : >> Date: Sun Jul 25 04:19:05 2010
> : >> New Revision: 210460
> : >> URL: http://svn.freebsd.org/changeset/base/210460
> : >>
> : >> Log:
> : >>  Get N64 building by defining VM_FREELIST_DIRECT to be
> : >>  VM_FREELIST_DEFAULT.  I believe this is correct, since KX is set in
> : >>  n64, and thus all RAM can be direct mapped.
> : 
> : Thanks, this is something I missed in my MIPS page table changes.
> : 
> : >
> : > Yes, it is.
> : 
> : In MIPS 64bit, whole physical memory is direct mapped thru a XKPHYS
> : region. We can use vm_page_alloc() for pmap_alloc_pte_page() and
> : VM_WAIT for pmap_grow_pte_page_cache(), is this something we should
> : consider?
>
> Likely.  Any idea what kind of performance difference this would buy
> us?
>   

As long as n64 has a single free list, there is no point in changing 
pmap_alloc_pte_page() to use vm_page_alloc().  There may, however, be 
some point to using VM_WAIT in pmap_grow_pte_page_cache(), because 
vm_contig_grow_cache() is far more aggressive about paging out dirty 
pages than VM_WAIT is, and VM_WAIT would suffice.

For what it's worth, fixing pmap_change_wiring() and 
pmap_page_wired_mappings() is almost certainly more important.

Alan