On Tue, Apr 19, 2011 at 03:38:14AM +0900, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa <yoshikawa.tak...@oss.ntt.co.jp>
>
> We optimize multi level guest page table walk as follows:
>
> 1. We cache the memslot which, probably, includes the next guest page
> tables to avoid searching for it many times.
> 2. We use get_user() instead of copy_from_user().
>
> Note that this is kind of a restricted way of Xiao's more generic
> work: "KVM: optimize memslots searching and cache GPN to GFN."
>
> With this patch applied, paging64_walk_addr_generic() has improved
> as the following tracing results show.
>
> Before:
> 3.169 us | paging64_walk_addr_generic();
> 1.880 us | paging64_walk_addr_generic();
> 1.243 us | paging64_walk_addr_generic();
> 1.517 us | paging64_walk_addr_generic();
> 3.009 us | paging64_walk_addr_generic();
> 1.814 us | paging64_walk_addr_generic();
> 1.340 us | paging64_walk_addr_generic();
> 1.659 us | paging64_walk_addr_generic();
> 1.748 us | paging64_walk_addr_generic();
> 1.488 us | paging64_walk_addr_generic();
>
> After:
> 1.714 us | paging64_walk_addr_generic();
> 0.806 us | paging64_walk_addr_generic();
> 0.664 us | paging64_walk_addr_generic();
> 0.619 us | paging64_walk_addr_generic();
> 0.645 us | paging64_walk_addr_generic();
> 0.605 us | paging64_walk_addr_generic();
> 1.388 us | paging64_walk_addr_generic();
> 0.753 us | paging64_walk_addr_generic();
> 0.594 us | paging64_walk_addr_generic();
> 0.833 us | paging64_walk_addr_generic();
Nice optimization! What scenarios have you used to test it?
Joerg
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