Firstly, on advice in a previous post, I have switched the search index updating to out-of-hours so that is not the problem.
Here is my analysis of what is going on.
Awasu is presented with 100 feeds that are due for a refresh - this can happen in several ways: Import an OPML file, start Awasu in the morning, Awasu wakes up after observing the blackout time, or a large number of feeds become due a refresh at the same time. The former causes the latter.
As it stands, Awasu is taking between 10 and 20 minutes to update my feeds, which are all firing off at two-hour intervals - maybe I should change some of them? During this time my machine becomes unusable. Time to make a coffee!
How I would fix this.
Introduce a random element. In the first three scenarios above, when Awasu is presented with a large number of feeds to update at once it should schedule them randomly throughout the next hour. This then fixes the last scenario as the feeds then update in two-hour intervals based on their last update, which was randomly scheduled. This spreads the load throughout the day. An impatient user can then override this by selecting Update All Channels or forcing an update on specific channels.