Here are the last 6 queries killed by mysql

2014-07-23 03:41:47 +0000 [info] killed_thread_id:10652460 user:geobo2mp_social host:localhost db:geobo2mp_social command:Sleep time:21 query:2014-07-23 11:45:35 +0000 [info] killed_thread_id:10822468 user:geobo2mp_social host:localhost db:geobo2mp_social command:Sleep time:19 query:2014-07-23 13:00:27 +0000 [info] killed_thread_id:10851978 user:geobo2mp_social host:localhost db:geobo2mp_social command:Sleep time:17 query:2014-07-23 13:59:35 +0000 [info] killed_thread_id:10872313 user:DELAYED host:localhost db:geobo2mp_social command:Delayed insert time:21 query:2014-07-23 14:06:31 +0000 [info] killed_thread_id:10874443 user:DELAYED host:localhost db:geobo2mp_social command:Delayed insert time:18 query:2014-07-23 17:58:55 +0000 [info] killed_thread_id:10955365 user:DELAYED host:localhost db:geobo2mp_social command:Delayed insert time:17 query:

Any idea, why is it happening? It seems these are the reason my cpu usage is spiking.