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    SubjectRE: Frontswap [PATCH 0/4] (was Transcendent Memory): overview
    > > So there are two users of frontswap for which the synchronous
    > > interface makes sense. I believe there may be more in the
    > > future and you disagree but, as Jeremy said, "a general Linux
    > > principle is not to overdesign interfaces for hypothetical users,
    > > only for real needs." We have demonstrated there is a need
    > > with at least two users so the debate is only whether the
    > > number of users is two or more than two.
    > >
    > > Frontswap is a very non-invasive patch and is very cleanly
    > > layered so that if it is not in the presence of either of
    > > the intended "users", it can be turned off in many different
    > > ways with zero overhead (CONFIG'ed off) or extremely small overhead
    > > (frontswap_ops is never set; or frontswap_ops is set but the
    > > underlying hypervisor doesn't support it so frontswap_poolid
    > > never gets set).
    >
    > Yet there are less invasive solutions available, like 'add trim
    > operation to swap_ops'.

    As Nitin pointed out much earlier in this thread:

    "No: trim or discard is not useful"

    I also think that trim does not do anything for the widely
    varying dynamically changing size that frontswap provides.

    > So what needs to be said here is 'frontswap is XX times faster than
    > swap_ops based solution on workload YY'.

    Are you asking me to demonstrate that swap-to-hypervisor-RAM is
    faster than swap-to-disk?



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