Messages in this thread | | | Date | Wed, 02 May 2007 12:19:27 -0700 | From | Zachary Amsden <> | Subject | Re: [patches] [PATCH] [28/34] i386: pte xchg optimization |
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Andi Kleen wrote: >> I always wondered why the xchg is necessary here at all. If the process of >> tearing down a page table entry has started, other users of the mapped >> linear address are broken anyway - why is it necessary to still monitor the >> effect they may have on the A/D bits, unless this is a transient tear down? >> >> Checking for the uses of ptep_get_and_clear, I would judge that the use in >> change_pte_range() may in fact need the xchg, but the uses in >> vunmap_pte_range() and zap_pte_range() shouldn't. >> > > Yes I agree. Might be a nice speed up for exit to distingush the cases. >
That is what I did in this patch - but with care zap_pte_range can also be called in non-teardown cases when unmapping (when !fullmm) and user mappings could still be in effect on remote processors.
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