Last evening I spend quite a lot of time figuring out why tomcat was consuming 90% of CPU and ksoftirqd was consuming the rest of cpu. Typically tomcat uses all of the CPU when has gone out of memory (PermGen). So I restarted tomcat but cpu gone up to 100% immediately. After various attempts i saw that ksoftirqd was consuming 10% and the total consumed cpu was like after a DOS attack:4 root 20 0 0 0 0 S 0.0 0.0 567:44.72 ksoftirqd/0
I found no DoS signs in the rest of the system, googling arround i found "the leap second issue". A kernel issue related to a second added between 30 June and 1 July. This is the post: http://www.mail-archive.com/user@cassandra.apache.org/msg23474.html In fact this command linedate; date `date +"%m%d%H%M%C%y.%S"`; date
Reduced the cpu usage from 100% to the usual 5%
This is the related CPU load graph: