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    SubjectRe: [openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation
    On Wed, 11 May 2005, William Jordan wrote:
    > On 5/7/05, Hugh Dickins <> wrote:
    > > > My understanding is that mlock() could in theory allow the page to be moved,
    > > > but that currently nothing in the kernel would actually move it. However,
    > > > that could change in the future to allow hot-swapping of RAM.
    > >
    > > That's my understanding too, that nothing currently does so. Aside from
    > > hot-swapping RAM, there's also a need to be able to migrate pages around
    > > RAM, either to unfragment memory allowing higher-order allocations to
    > > succeed more often, or to get around extreme dmamem/normal-mem/highmem
    > > imbalances without dedicating huge reserves. Those would more often
    > > succeed if uninhibited by mlock.
    > If I am reading you correctly, you are saying that mlock currently
    > prevents pages from migrating around to unfragment memory, but
    > get_user_pages does not prevent this?

    No, not what I meant at all. I'm saying that currently (aside from
    proposed patches) there is no such migration of pages; that we'd prefer
    to implement migration in such a way that mlock does not inhibit it
    (though there might prove to be strong arguments defeating that);
    and that get_user_pages _must_ prevent migration (and if there
    were already such migration, I'd be saying it _does_ prevent it).

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      Last update: 2005-05-11 22:47    [W:0.032 / U:19.896 seconds]
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