Messages in this thread | | | Date | Fri, 28 May 2010 21:12:36 -0500 | From | "Jayson R. King" <> | Subject | Re: [PATCH 2.6.27.y 2/3] ext4: Fix file fragmentation during large file write. |
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On 05/28/2010 08:06 PM, tytso@mit.edu wrote: > On Fri, May 28, 2010 at 02:26:57PM -0500, Jayson R. King wrote: >> From: Aneesh Kumar K.V<aneesh.kumar@linux.vnet.ibm.com> >> 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 minutes.
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.
Rgds,
Jayson
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