Re: page fault scalability patch V12 [0/7]: Overview and performance tests

From: Nick Piggin
Date: Thu Dec 09 2004 - 23:56:21 EST


Nick Piggin wrote:

Yep, the update_mmu_cache issue is real. There is a parallel problem
that is update_mmu_cache can be called on a pte who's page has since
been evicted and reused. Again, that looks safe on IA64, but maybe
not on other architectures.

It can be solved by moving lru_cache_add to after update_mmu_cache in
all cases but the "update accessed bit" type fault. I solved that by
simply defining that out for architectures that don't need it - a raced
fault will simply get repeated if need be.


The page-freed-before-update_mmu_cache issue can be solved in that way,
not the set_pte and update_mmu_cache not performed under the same ptl
section issue that you raised.
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