I'd personally try sending it a HUP signal:
run top, note the PID, then:
kill -HUP 1234
Where 1234 is the PID.
If that doesn't work, send it a term, and then last resort, if term doesn't stop it, kill it:
kill -15 1234
kill -9 1234
Then check your logs. See what the problem was, and what killing it did. Also, look at your crons and see how often logrotate is supposed to run. If it's every minute maybe consider changing that to once a week or even once a month.