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    SubjectRe: -mm merge plans for 2.6.23
    On Wed, 25 Jul 2007 23:33:24 -0700 "Ray Lee" <ray-lk@madrabbit.org> wrote:

    > > So. We can
    > >
    > > a) provide a way for userspace to reload pagecache and
    > >
    > > b) merge maps2 (once it's finished) (pokes mpm)
    > >
    > > and we're done?
    >
    > Eh, dunno. Maybe?
    >
    > We're assuming we come up with an API for userspace to get
    > notifications of evictions (without polling, though poll() would be
    > fine -- you know what I mean), and an API for re-victing those things
    > on demand.

    I was assuming that polling would work OK. I expect it would.

    > If you think that adding that API and maintaining it is
    > simpler/better than including a variation on the above hueristic I
    > offered, then yeah, I guess we are. It'll all have that vague
    > userspace s2ram odor about it, but I'm sure it could be made to work.

    Actually, I overdesigned the API, I suspect. What we _could_ do is to
    provide a way of allowing userspace to say "pretend process A touched page
    B": adopt its mm and go touch the page. We in fact already have that:
    PTRACE_PEEKTEXT.

    So I suspect this could all be done by polling maps2 and using PEEKTEXT.
    The tricky part would be working out when to poll, and when to reestablish.

    A neater implementation than PEEKTEXT would be to make the maps2 files
    writeable(!) so as a party trick you could tar 'em up and then, when you
    want to reestablish firefox's previous working set, do a untar in
    /proc/$(pidof firefox)/

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