I have similar issue. Mysqld task hits 100% on random basis. And it comes back to normal state only after mysql restart.
It was fine for a long time, and this problem just appeared several days ago. Now I have to restart mysql almost every hour.
And this happens on production system.
Usually CPU usage start increasing gradually and reaches 100% in several minutes.
It happens more often if I use admin UI.
I am not mysql pro and have no ideas how to stop or monitor this.
Does anybody have similar issues? Will appreciate any help!
Solved by disabling RSS.
I located bad SELECT by using
But it was no time to locate exactly what RSS causes this (I gues - new products feed).
mysqladmin -p processlist