Zero Pages / Cache Coherency

[Adrian Cox]

I'm currently trying out the pre-zeroing of pages in the idle task, and
I'm a little worried about its effect on cache-coherency. I can't prove
to
my satisfaction that none of the pages being cleared by zero_paged() is
in the cache, and I'm not sure that turning off caching in the PTE will
have any effect on cache lines already allocated in L1 or L2.

Obviously, any incoherency would be extremely rare, but ensuring that
the page is invalidated from the caches before it is zeroed has the
added bonus of removing the need for a flush_page_to_ram() in my
modified anonymous memory allocator.

Any comments? 

- Adrian Cox, AG Electronics

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