What does MySQL waste system resources on if there are no queries?

Question

MySQL

Given: a newly started MySQL daemon that has not yet received a single request and no attempt to establish a session. The work of the DBMS was completed normally last time, no recovery processes are taking place. The binlog is empty (106 bytes). However, top shows that the mysqld process is eating 100% WCPU.

This continues for 5-10 minutes, then the load drops to the expected zero. If you log in during this period and look at SHOW FULL PROCESSLIST, there is nothing there. So what does MySQL do?

MySQL: 5.1.57-log from FreeBSD port: mysql-server-5.1.57
OS: amd64 FreeBSD 8.0-RELEASE

Answer 1

Most likely stuffs caches or checks tables.
See logs. Everything should be described there.

Answer 2

run gdb at the moment of flashing
make attach to the hung process
execute thread apply all bt full
voila - I think the whole list of actions
will really fill the table cache, some system process, but guess it with a pitchfork in the water - die, then tell me.

Answer 3

also look at iotop, maybe you will see something there.

Answer 4

Do you happen to have Archive tables? MySQL at startup always checks them, which is 10-15 minutes of 100% CPU usage. For a large innodb, it can load / buffer pool indexes into memory, see at the same time how memory usage changes