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    SubjectRe: [PATCH -mm 00/25] VM pageout scalability improvements (V10)
    On Fri, 6 Jun 2008 14:02:16 -0700
    Andrew Morton <> wrote:
    > On Fri, 06 Jun 2008 16:28:38 -0400
    > Rik van Riel <> wrote:
    > > On large memory systems, the VM can spend way too much time scanning
    > > through pages that it cannot (or should not) evict from memory. Not
    > > only does it use up CPU time, but it also provokes lock contention
    > > and can leave large systems under memory presure in a catatonic state.
    > >
    > > Against 2.6.26-rc2-mm1
    > >
    > > This patch series improves VM scalability by:
    > -mm has a patch called
    > vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
    > which has been sitting there for some time waiting for us to work out
    > whether or not it is a desirable thing.
    > This patchset of yours apparently retains the change which
    > vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
    > makes.
    > But do we know that it was a good one?

    Benchmark results here indicate that it helps some workloads by up
    to 10%, but makes the page cache pages that fall off of the active
    list more prone to being replaced by streaming IO.

    I have added in a fix in this series to set the referenced bit on
    unmapped page cache pages that get deactivated, so that defect is

    I've been busy with some other stuff this week; I'll try to get
    you some numbers ASAP.

    All rights reversed.

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