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    SubjectRe: [RFC PATCH 0/4] (Take 2): transcendent memory ("tmem") for Linux
    Avi Kivity wrote:
    > In fact CMM2 is much more intrusive (but on the other hand provides
    > much more information).
    I don't think this will remain true long term. CMM2 touches a lot of
    core mm code and certainly qualifies as intrusive. However the result
    is that the VMM has a tremendous amount of insight into how the guest is
    using it's memory and can implement all sorts of fancy policy for
    reclaim. Since the reclaim policy can evolve without any additional
    assistance from the guest, the guest doesn't have to change as policy

    Since tmem requires that reclaim policy is implemented within the guest,
    I think in the long term, tmem will have to touch a broad number of
    places within Linux. Beside the core mm, the first round of patches
    already touch filesystems (just ext3 to start out with). To truly be
    effective, tmem would have to be a first class kernel citizen and I
    suspect a lot of code would have to be aware of it.

    So while CMM2 does a lot of code no one wants to touch, I think in the
    long term it would remain relatively well contained compared to tmem
    which will steadily increase in complexity within the guest.


    Anthony Liguori

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