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

[Christian Brandes]

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.

Thanks and best regards
Christian

--- original mail: ---

> could you reproduce the phenomenon?

>> Could you just try to reproduce that on a precise system?

>>> I would expect to find that in older kernels other threads are taking on the load.  Presumably they are flushing pages like mad to make space in cache for your workload. I guess I am asking, is the overall load actually higher, or just moved.

>>>> When I do "dd if=/dev/zero of=/tmp/zero1.tmp bs=1024 count=13000000" kworker threads start eating up my CPU-time as described in: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/887793 posting 22 and 23.
>>>> Older kernel versions do not seam to be affected like 3.0.0-13-generic.