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    SubjectRe: [patch][rfc][rft] vm throughput 2.4.2-ac4


    On Fri, 2 Mar 2001, Mike Galbraith wrote:

    > On Thu, 1 Mar 2001, Rik van Riel wrote:
    >
    > > > > The merging at the elevator level only works if the requests sent to
    > > > > it are right next to each other on disk. This means that randomly
    > > > > sending stuff to disk really DOES DESTROY PERFORMANCE and there's
    > > > > nothing the elevator could ever hope to do about that.
    > > >
    > > > True to some (very real) extent because of the limited buffering
    > > > of requests. However, I can not find any useful information
    > > > that the vm is using to guarantee the IT does not destroy
    > > > performance by your own definition.
    > >
    > > Indeed. IMHO we should fix this by putting explicit IO
    > > clustering in the ->writepage() functions.
    >
    > I notice there's a patch sitting in my mailbox.. think I'll go read
    > it and think (grunt grunt;) about this issue some more.

    Mike,

    One important information which is not being considered by
    page_launder() now the dirty buffers watermark.

    In general, it should not try to avoid writing dirty pages if we're above
    the dirty buffers watermark.

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