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    SubjectRe: [PATCH 2.6.27.y 2/3] ext4: Fix file fragmentation during large file write.
    On 05/28/2010 08:06 PM, wrote:
    > On Fri, May 28, 2010 at 02:26:57PM -0500, Jayson R. King wrote:
    >> From: Aneesh Kumar K.V<>
    >> Date: Thu Oct 16 10:10:36 2008 -0400
    >> Subject: ext4: Fix file fragmentation during large file write.
    >> commit 22208dedbd7626e5fc4339c417f8d24cc21f79d7 upstream.
    >> The range_cyclic writeback mode uses the address_space writeback_index
    >> as the start index for writeback. With delayed allocation we were
    >> updating writeback_index wrongly resulting in highly fragmented file.
    >> This patch reduces the number of extents reduced from 4000 to 27 for a
    >> 3GB file.
    > This isn't a critical bug fix either. I don't really care a whole
    > lot, since I don't plan to support ext4 with all of these patches but
    > if you haven't been doing a full set of testing with these patches,
    > I'd be very concerned about whether ext4 would be stable after
    > applying this patch series.
    > What sort of testing _have_ you done?

    I've ran dbench for hours on an ext4 volume followed by fsck on the
    volume. Without the patches (particularly, just the last patch, "ext4:
    Implement range_cyclic..."), a typical, sustained moderate to high ext4
    fs load on .27 would often lead to a deadlock. A good demonstration is
    to run "dbench 500" which will usually cause a deadlock in a couple of

    I wasn't aware of a way to apply the deadlock fix in "ext4: Implement
    range_cyclic..." without also introducing this patch, since some of the
    blocks it touches are created by this patch.

    Thanks for looking.



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