High processor activity after upgrade to 14.04

[phil1349]

I have just upgraded my laptop from 12.04 to 14.04, 12.04 has been running well for the past 18 months. I usually run the System Monitor tool so I can quickly check on system activity.

My laptop is a Lenovo Z580 with 6Gb RAM & an Intel 4-core i7 processor. With 12.04 even with several programs open at the same time the monitor indicated that all cores were running at less than 10% capacity unless there was a particularly intensive process taking place. Now I have upgraded to 14.04 all cores are now running at 30 - 40% even when all programs (except system monitor) are shut down. This is a problem as it causes the fan to run at high speed greatly reducing battery life.

I ran "ps -A" to see what was going on and noticed many entries of the form "17264 ? 00:00:00 kworker/u16:0"

The no at the end could be anything up to 100 and there can be up to 150 such entries. Any idea as to what kworker is & what does it do & why so many entries ? Is there any way to fix it ?

If it will help I can post the full listing from "ps -A" or any other info that may be relevant.

[bweinel]

Kworker is a kernel worker thread which performs a number of different kernel processes. Any number of different issues could be causing your slowdown. There have been some problems reported with the desktop search process causing slow preformance while searching the /home directory areas. (there is a thread at https://www.kubuntuforums.net/node/59323 on how to keep it from doing that.)

However your issue sounds more like a driver/device conflict of some type.

You might consider troubleshooting it using perf monitor in linux-tools. There's a good thread on how to go about that here.

cheers,
bill

[phil1349]

Thanks to bweinel for the advice, I tried that but it did not seem to make much difference. Processor activity is normal after a reboot and slowly builds up so I did dumps of ps -A to a text file at intervals to try to see what is going on. These indicated that kworker was definately quietly breeding away in the background. I also noticed that keuphoria.kss was also breeding like the proverbial. This is a process from the screensaver so I turned that off and manually killed of all the keuphoria threads and core activity dropped like a stone.

It seems therefore that the screensaver was the problem, I shall experiment a bit more with it but perhaps it should be reported as a bug.