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    SubjectRe: Frontswap [PATCH 0/4] (was Transcendent Memory): overview
    On 04/25/2010 03:41 AM, Dan Magenheimer wrote:
    >>> No, ANY put_page can fail, and this is a critical part of the API
    >>> that provides all of the flexibility for the hypervisor and all
    >>> the guests. (See previous reply.)
    >>>
    >> The guest isn't required to do any put_page()s. It can issue lots of
    >> them when memory is available, and keep them in the hypervisor forever.
    >> Failing new put_page()s isn't enough for a dynamic system, you need to
    >> be able to force the guest to give up some of its tmem.
    >>
    > Yes, indeed, this is true. That is why it is important for any
    > policy implemented behind frontswap to "bill" the guest if it
    > is attempting to keep frontswap pages in the hypervisor forever
    > and to prod the guest to reclaim them when it no longer needs
    > super-fast emergency swap space. The frontswap patch already includes
    > the kernel mechanism to enable this and the prodding can be implemented
    > by a guest daemon (of which there already exists an existence proof).
    >

    In this case you could use the same mechanism to stop new put_page()s?

    Seems frontswap is like a reverse balloon, where the balloon is in
    hypervisor space instead of the guest space.

    > (While devil's advocacy is always welcome, frontswap is NOT a
    > cool academic science project where these issues have not been
    > considered or tested.)
    >


    Good to know.

    --
    error compiling committee.c: too many arguments to function



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