Avg load goes up after upgrading to Mavericks

Finally found the culprit. I'm using zsh and the plugin vi-mode from Oh-my-zsh interacts poorly with git tools. Disabling the plugin made my zsh usable again in terms of responsiveness and reducing CPU load.

There are conflicting reports whether Apple's git needs to be upgraded and you can follow that process at https://github.com/robbyrussell/oh-my-zsh/issues/2189

Still many thanks for all the people reply to the answer.

It is probably spotlight reindexing your system. Look up in your activity monitor which process is using the most computing time:

Alternatively you can click on your battery icon to see this information.

The problem should be gone in decent time.

If you cannot isolate a process that is actually taking CPU time now that should not (or did not before), then two things might be getting mixed up here:

uptime and top load averages are run queue average depth and not necessarily synonymous with CPU loading.

Yes, you need threads on the queue to have any chance to load the CPU, but just because there are 4 programs on the queue on average over a minute, doesn't mean that those threads together need to consume even 1% of the CPU time.

The real answer here will be to look at output like ps aux to determine which processes are actually running as opposed to sleeping and combine that with iostat to watch the actual CPU loading and see if you can determine if some new processes are running and whether that is increasing or decreasing the IO and CPU load on the system.