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    Subject[RFC 0/7] Postphone reclaim laundry to write at high water marks
    One of the problems with reclaim writeout is that it occurs when memory in a
    zone is low. A particular bad problem can occur if memory in a zone is
    already low and now the first page that we encounter during reclaim is dirty.
    So the writeout function is called without the filesystem or device having
    much of a reserve that would allow further allocations. Triggering writeout
    of dirty pages early does not improve the memory situation since the actual
    writeout of the page is a relatively long process. The call to writepage
    will therefore not improve the low memory situation but make it worse
    because extra memory may be needed to get the device to write the page.

    This patchset fixes that issue by:

    1. First reclaiming non dirty pages. Dirty pages are deferred until reclaim
    has reestablished the high marks. Then all the dirty pages (the laundry)
    is written out.

    2. Reclaim is essentially complete during the writeout phase. So we remove
    PF_MEMALLOC and allow recursive reclaim if we still run into trouble
    during writeout.

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      Last update: 2007-08-20 23:55    [W:3.682 / U:0.212 seconds]
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