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    SubjectRe: [PATCH 11/11] mm: Isolate pages for immediate reclaim on their own LRU
    On Wed, Dec 14, 2011 at 03:41:33PM +0000, Mel Gorman wrote:
    > It was observed that scan rates from direct reclaim during tests
    > writing to both fast and slow storage were extraordinarily high. The
    > problem was that while pages were being marked for immediate reclaim
    > when writeback completed, the same pages were being encountered over
    > and over again during LRU scanning.
    >
    > This patch isolates file-backed pages that are to be reclaimed when
    > clean on their own LRU list.

    Excuse me if I sound like a broken record, but have those observations
    of high scan rates persisted with the per-zone dirty limits patchset?

    In my tests with pzd, the scan rates went down considerably together
    with the immediate reclaim / vmscan writes.

    Our dirty limits are pretty low - if reclaim keeps shuffling through
    dirty pages, where are the 80% reclaimable pages?! To me, this sounds
    like the unfair distribution of dirty pages among zones again. Is
    there are a different explanation that I missed?

    PS: It also seems a bit out of place in this series...?


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