What do the mysqlds do in my mysql database? I build a wordpress on my localhost,and local pc can't connect with internet.
To login mysql database with command.

mysql -u root -p
mysql&gt; show processlist;
+-----+------+-----------+------------+---------+------+-------+------------------+
| Id  | User | Host      | db         | Command | Time | State | Info             |
+-----+------+-----------+------------+---------+------+-------+------------------+
| 385 | root | localhost | wpdatabase | Query   |    0 | NULL  | show processlist |
+-----+------+-----------+------------+---------+------+-------+------------------+
1 row in set (0.00 sec)

sudo pstree -pl  795
mysqld_safe(795)───mysqld(1188)─┬─{mysqld}(1286)
                                ├─{mysqld}(1287)
                                ├─{mysqld}(1288)
                                ├─{mysqld}(1289)
                                ├─{mysqld}(1290)
                                ├─{mysqld}(1291)
                                ├─{mysqld}(1292)
                                ├─{mysqld}(1293)
                                ├─{mysqld}(1294)
                                ├─{mysqld}(1295)
                                ├─{mysqld}(1385)
                                ├─{mysqld}(1386)
                                ├─{mysqld}(1387)
                                ├─{mysqld}(1388)
                                ├─{mysqld}(1403)
                                ├─{mysqld}(1420)
                                ├─{mysqld}(3435)
                                └─{mysqld}(22796)


There are so many mysqlds ,why show processlist can't list it?
I see 18 mysqld's there.  I'll bet SHOW VARIABLES LIKE 'thread_cache_size'; gives you at least 18.  And, I'll bet that, at some point since startup, you had 18 clients running.

So why doesn't PROCESSLIST show 18 processes/threads?  Because wait_timeout killed off 17 of them.

Bottom line:  Nothing to worry about.