Messages in this thread | | | Date | Tue, 5 May 2015 18:29:55 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH 02/13] KVM: reuse memslot in kvm_write_guest_page |
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2015-05-05 11:03-0400, Bandan Das: > Paolo Bonzini <pbonzini@redhat.com> writes: > >> From: Radim Krčmář <rkrcmar@redhat.com> >> >> Saves one O(log N) search. > > It really doesn't hurt to change this to: > "Caching memslot value helps us avoid another O(log N) search > later when calling mark_page_dirty_in_slot()." > > Sorry I am not a fan of commit messages less than 75 characters :)
Sure, I just couldn't find a message that would be easier to understand than the code and not misleading at the same time ... what came out was a teaser for people who care about performance :)
In verbose mode, I'd write it like this: gfn_to_hva() and mark_page_dirty() both call gfn_to_memslot(). We can store a result of gfn_to_memslot() (memslot) and unwrap gfn_to_hva() and mark_page_dirty() to directly call functions that accept a memslot. gfn_to_memslot() does a binary search, so it also saves some cycles.
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