On Thu, Aug 05, 2010 at 11:31:00AM +0200, Dominik Brodowski wrote: > Hey, > > when attempting to track down insufficient I/O performance, I found the > following reression relating to direct-io on my notebook, where an > ata device, which consists of several partitions, is combined to a lvm > volume, and one logical volume is then encrypted using dm-crypt. Test case > was the following command: > > $ dd if=/dev/mapper/vg0-root_crypt of=/dev/zero iflag=direct bs=8k count=131072 > > 2.6.34 results in ~16 MB/s, > 2.6.35 results in ~ 3.1 MB/s > > The regression was bisected down to the follwoing commit: > > commit c2c6ca417e2db7a519e6e92c82f4a933d940d076 > Author: Josef Bacik <josef@xxxxxxxxxx> > Date: Sun May 23 11:00:55 2010 -0400 > > direct-io: do not merge logically non-contiguous requests > > ... > > How to fix this? I do not use btrfs, but ext3 (and the access was down on > the block level, not on the fs level, so this btrs-related commit should not > cause such a regression). Well, you've already bisected down to an offending if statement, that's a huge help. I'll try to reproduce this and fix it up today. But, I'm surprised your drive is doing 8K dio reads at 16MB/s, that seems a little high. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
