On Mon, Jun 06, 2011 at 12:43:10PM -0400, micah anderson wrote: > > 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 Oh, I bet I know what's going on. Ext3 defaults to barriers being off. Ext4 defaults to barriers turned on, which is safer if you have power drops. If you have a UPS and are confident that the UPS monitoring software is properly setup so the system will go through a controlled, clean shutdown when the UPS power is running low, then you could consider disabling barriers on ext4 without committing professional sysadmin malpractice. :-) Since mail systems tend to be very fsync() happy, and fsyncs() translate to barriers, that's probably the explanation of what's going on here. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
