HELP! Just 5 minutes! - kworker eating up cpu time when doing dd on 3.2.0 kernels

[Andy Whitcroft]

On Mon, Feb 06, 2012 at 10:53:04AM +0100, Christian Brandes wrote:
> Hi all!
> 
> This takes just 5 minutes!!!!!
> Please, could someone help me!
> 
> It looks like a serious bug in 3.2-Kernels.
> 
> Could someone just do "dd if=/dev/zero of=/tmp/zero1.tmp bs=1024 count=13000000" on a precise system with 3.2. kernel and watch CPU usage of kworker threads going up when cache memory is filled up.

Nope could not reproduce it here on a machine with only 2GB of ram; this
is with a 3.2.0-12 Ubuntu kernel.  I see the expected kswapd0 and flush-8:0
using some 10% between them worst case.  Which kernel are you using,
what platform is triggering it.

-apw