On Fri, 3 Jun 2011 23:09:49 -0400, Ted Ts'o <tytso@xxxxxxx> wrote: > On Fri, Jun 03, 2011 at 05:49:17PM -0400, Micah Anderson wrote: > > However, ever since I did that change, I've noticed an increase in I/O > > wait state on the CPUs. I've been trying to determine why, and if there > > were some things I should tune on this ext4 filesystem. > > How are you measuring this? Through munin graphs, unfortunately we don't have a lot of data from before the change, but you can see the jump early on in this graph, where the change was made: http://lackof.org/~taggart/tmp/willet-cpu-year.png I'll note that we also moved to squeeze from lenny at this time. Basically we decided to move to squeeze and then convert to ext4, so that throws in some other variables here too. As I mentioned before, this is a high traffic mailing list system, which does a lot of I/O. We're also seeing lots of rescheduling interrupts after the upgrade to the squeeze kernel: http://lackof.org/~taggart/tmp/willet-irqstats-year.png (see the jump in the pink line on the left side?) Searches on "rescheduling interrupts" finds lots of people using powertop to try to reduce their laptop power usage (this might be related: https://help.ubuntu.com/community/ReschedulingInterrupts), I'm wondering if maybe there were changes from lenny to squeeze to try and optimize for that, but are hurting in our case. micah
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