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    SubjectRe: PATCH: killing read_ahead[]
    Linus Torvalds wrote:
    >
    > On Wed, 25 Oct 2000, Rik van Riel wrote:
    > >
    > > OTOH, block-dev readahead makes sense for filesystems where
    > > the packing locality is close to the access pattern BUT NOT
    > > close to anything the page cache would recognise as being
    > > close.
    >
    > I dunno. The main reason I'd like to get the block devices into the page
    > cache is that right now there is no way to mmap them - something that can
    > potentially be _very_ useful, regardless of readahead.
    >
    > And quite frankly, the generic file readahead has been pounded upon and
    > tested a lot more than the block device read-ahead ever was. I bet it
    > performs better if for no other reason.

    And then of course the FS is the LOGICAL level of access to the device -
    so
    if read ahead matters then it's this level where it should happen -
    since
    this is the place where actual predictability of the next access
    (actually
    the assumption that the access will happen at least semi-sequentially)
    has good
    chances to be right. So you are completely right that the page-cache is
    the right place where the rahead logic should take place. I have just
    filled
    the argumentation gap ;-).

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