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SubjectRe: [PATCH] mm: Flush the TLB for a single address in a huge page
On 07/22/2015 03:48 PM, Catalin Marinas wrote:
> You are right, on x86 the tlb_single_page_flush_ceiling seems to be
> 33, so for an HPAGE_SIZE range the code does a local_flush_tlb()
> always. I would say a single page TLB flush is more efficient than a
> whole TLB flush but I'm not familiar enough with x86.

The last time I looked, the instruction to invalidate a single page is
more expensive than the instruction to flush the entire TLB. We also
don't bother doing ranged flushes _ever_ for hugetlbfs TLB
invalidations, but that was just because the work done around commit
e7b52ffd4 didn't see any benefit.

That said, I can't imagine this will hurt anything. We also have TLBs
that can mix 2M and 4k pages and I don't think we did back when we put
that code in originally.



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