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    SubjectRe: [RFC PATCH V2 5/5] vhost: access vq metadata through kernel virtual address
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    On 2019/3/12 上午11:50, Michael S. Tsirkin wrote:
    >>>> Using direct mapping (I
    >>>> guess kernel will always try hugepage for that?) should be better and we can
    >>>> even use it for the data transfer not only for the metadata.
    >>>>
    >>>> Thanks
    >>> We can't really. The big issue is get user pages. Doing that on data
    >>> path will be slower than copyXuser.
    >> I meant if we can find a way to avoid doing gup in datapath. E.g vhost
    >> maintain a range tree and add or remove ranges through MMU notifier. Then in
    >> datapath, if we find the range, then use direct mapping otherwise
    >> copy_to_user().
    >>
    >> Thanks
    > We can try. But I'm not sure there's any reason to think there's any
    > locality there.
    >

    Ok, but what kind of locality do you mean here?

    Thanks

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