I've got munin monitoring virtual private server. And here're graphs for context switches:
By day: http://imgur.com/ljon5.gif
What could have caused this? I'm not worried about the pike, because it can be explained with heavy load which is confirmed by other graphs. But what about flatline? It looks like several days with zero switches, then it magically turns back on. And now it's off again. Any advice on where to look is greatly appreciated.
Did what-ever service is monitoring the stats fall over and is in need of restarting? It could be that your grapher sees "no reading" as a zero reading.