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    SubjectRe: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim
    On 07/19/2010 09:11 AM, Mel Gorman wrote:
    > When memory is under enough pressure, a process may enter direct
    > reclaim to free pages in the same manner kswapd does. If a dirty page is
    > encountered during the scan, this page is written to backing storage using
    > mapping->writepage. This can result in very deep call stacks, particularly
    > if the target storage or filesystem are complex. It has already been observed
    > on XFS that the stack overflows but the problem is not XFS-specific.
    > This patch prevents direct reclaim writing back filesystem pages by checking
    > if current is kswapd or the page is anonymous before writing back. If the
    > dirty pages cannot be written back, they are placed back on the LRU lists
    > for either background writing by the BDI threads or kswapd. If in direct
    > lumpy reclaim and dirty pages are encountered, the process will stall for
    > the background flusher before trying to reclaim the pages again.
    > As the call-chain for writing anonymous pages is not expected to be deep
    > and they are not cleaned by flusher threads, anonymous pages are still
    > written back in direct reclaim.
    > Signed-off-by: Mel Gorman<>

    Acked-by: Rik van Riel <>

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      Last update: 2010-07-19 20:29    [W:0.019 / U:34.820 seconds]
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