ext4: Fix file fragmentation during large file write.
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From: tytso on 28 May 2010 21:10 On Fri, May 28, 2010 at 02:26:57PM -0500, Jayson R. King wrote: > From: Aneesh Kumar K.V <aneesh.kumar(a)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? - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Jayson R. King on 28 May 2010 22:50
On 05/28/2010 08:06 PM, tytso(a)mit.edu wrote: > On Fri, May 28, 2010 at 02:26:57PM -0500, Jayson R. King wrote: >> From: Aneesh Kumar K.V<aneesh.kumar(a)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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |