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SubjectRe: [PATCH 4/7] KVM: sort memslots and use binary search to search the right slot
On 02/22/2011 10:25 PM, Avi Kivity wrote:
> On 02/22/2011 10:12 AM, Xiao Guangrong wrote:
>> Sort memslots then search the slot with binary search to speed up the
>> slot searching
>>
>
> I'm not sure if a binary search is the right algorithm here. It introduces a lot of branches which may be mispredicted.
>
> Options we've discussed are:
>
> - Sort slots by size, use linear search (so the largest slots are found quickly)
> - Weighted balanced tree http://en.wikipedia.org/wiki/Weight-balanced_tree, use weight == slot size
>

Yeah, there are the better chooses.

> Both options still make the miss case (mmio) slow. We could cache the result of a miss in an spte by using a reserved bit, and checking the page fault error code (or seeing if we get an ept violation or ept misconfiguration), so if we get repeated mmio on a page, we don't need to search the slot list/tree.
>

Sounds good! Will do it, thanks!



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