"kworker" is a placeholder process for kernel worker threads, which
perform most of the actual processing for the kernel, especially in
cases where there are interrupts, timers, I/O, etc. These typically
correspond to the vast majority of any allocated "system" time to
running processes. It is not something that can be safely removed from
the system in any way, and is completely unrelated to nepomuk or KDE
(except in that these programs may make system calls, which may
require the kernel to do something).
I found this on a Ask Ubuntu question found here. Apparently the dude's solution at that question was I solved the problem by installing
phc-intel packages from link
Some interesting information regarding what kworker is and its usage can be found here. Unfortunately, the solution there seems to be a future kernel upgrade.
From the same question:
I've found many reports of something that "fixed" this for one or
another user. Most "fixes" seem to be related to updates of the kernel
of various sorts. Where the update can be tracked to a specific issue,
it seems to often be some driver or kernel service that has been
patched to not misbehave: I have the impression that there are a very
large number of things in the kernel that can cause a behaviour which
is observed as excessive kworker usage.
If you find the system unusable due to excessive kworker activity, I
would recommend trying to do fewer things. If you think you're not
doing anything, try shutting down long-running services or timers (RSS
readers, mail readers, file indexers, activity trackers, etc.). If
this doesn't work, try restarting. If your system allows you to enable
or disable hardware in a preboot environment, try turning off hardware
you aren't using. If it happens on every restart before you do
anything, you could try uninstalling things, but at this point you'll
want to be running syscall profiling tools to track down specific
applications that seem to be causing this overload.