Re: High CPU usage / load average after upgrading to Ubuntu 12.04

On Mon, Feb 18, 2013 at 6:39 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> Scott,
>
>> So do you have generally slow IO, or is it fsync behavior etc?
>
> All tests except pgBench show this system as superfast. Bonnie++ and DD
> tests are good (200 to 300mb/s), and test_fsync shows 14K/second.
> Basically it has no issues until checkpoint kicks in, at which time the
> entire system basically halts for the duration of the checkpoint.
>
> For that matter, if I run a pgbench and halt it just before checkpoint
> kicks in, I get around 12000TPS, which is what I'd expect on this system.
>
> At this point, we've tried 3.2.0.26, 3.2.0.27, 3.4.0, and tried updating
> the RAID driver, and changing the IO scheduler. Nothing seems to affect
> the behavior. Testing using Ext4 (instead of XFS) next.

Did you try turning barriers on or off *manually* (explicitly)? With
LSI and barriers *on* and ext4 I had less-optimal performance. With
Linux MD or (some) 3Ware configurations I had no performance hit.

--
Jon