svn commit: r245147 - head/sys/arm/include

[Konstantin Belousov]

On Tue, Jan 08, 2013 at 10:01:11AM -0700, Ian Lepore wrote:
> I'm just learning the armv6/v7 stuff myself right now, but I can answer
> your question for our current armv4/v5 implementation...
> 
> When there is more than one mapping of a page in v4/v5 and any one of
> those mappings is writable, then the pmap.c code changes all existing
> mappings to be uncacheable to maintain coherency.  If the writable
> mapping is removed and all that remains are read/exec mappings, the
> existing mappings are made cacheable again.  Yes, that's just as
> inefficient and expensive as it sounds.  :)

Interesting, so the arm/pmap.c in fact maintain pv entries even for the
unmanaged pages and kernel mappings ? But this approach, requiring pv
entries for the kernel mappings, makes kernel pv entries non-reclamable
on the low memory condition. In fact, I cannot find any traces of the pv
reclaim in the arm/pmap.c.
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