mounted external ext4 causes "high" kworker cpu

[Chris Murphy]

On Apr 27, 2012, at 9:53 AM, Jeff Moyer wrote:

> Chris Murphy <lists at colorremedies.com> writes:
> 
>> Normally top reports CPU line, sy at 0.4% when idle. If I format an
>> external Firewire disk as btrfs and mount it, it remains at 0.4%. If I
>> reformat as XFS and mount it, again top reports sy at 0.4%. However,
>> if I reformat as ext4 and mount it, sy runs at 3.5%. These two
>> processes are now at the top of top's results:
>> 
>> kworker/1:2
>> kworker/0:4
>> 
>> Each uses on average 1.9% CPU. The light on the external drive flashes
>> 4x per second. There are no processes using the disk at all while this
>> is going on. If I umount it, the pulsing stops. If I remount it, the
>> pulsing resumes as does the slightly higher CPU consumption.
>> 
>> This doesn't happen with the same hardware mounted XFS or btrfs or
>> HFS+.
>> 
>> Odd?
> 
> Sounds like lazy itable init.  Try mkfs -t ext4 -E lazy_itable_init=0.

This is happening on internal disks, targeted for Fedora installation. I can hear it once install is complete, still booted from DVD media. Is this a bug?

Chris Murphy