My hardware:
Macbook pro 11,1 (late 2013). x86-64 processor.

There is a process called kworker that constantly consumes 70% of one of my cores and around 20% of my total processor.

Issue was resolved when I downgraded to an earlier version of the kernel that I had installed (version 3.11.10-301).

Any one has an idea what should I do to get back to the new kernel?

Have you looked in /var/log/syslog to see if there's something in there constantly retrying and failing? Going from 3.10.17 incrementally to 3.16.2, currently, I noticed a lot of changes in udevd behaviour, with 3.15.5+ hanging for 30 seconds on boot.

syslog showed a lot of retries of hardware and networks that weren't ready yet. The older kernels certainly seemed nippier too, although I haven't tried benchmarking to nail it down. Perhaps you have something like that going on. The other thing is, your kernel .config is probably different, did you compile it yourself with the old .config as a starting point and then with make mrproper make oldconfig?

hi mostly harmless
thanks for the reply. to be honest I don't know how to decode logs (I'm a noob).
and no I didn't compile it myself, I just got it off the repos with yum.

I've reported this bug here

There is a temporary fix is to the issue

That would seem to be an appropriate circumvention in this case . . .

I would simply continue to run the kernel that does not exhibit this problem, until the problem-report that you have filed has been investigated and fixed. It would clearly seem that something is now failing to properly-clear an interrupt. It could easily trace back to some device-driver somewhere. But that isn't your problem.