[mysqld]
# ...
log_output = 'FILE,TABLE';
slow_query_log = ON
long_query_time = 0.001

set global log_output = 'FILE,TABLE';
set global slow_query_log = 'ON';
set global long_query_time =0.001;

select * from `mysql`.slow_log

➜ mysqldumpslow --help
Usage: mysqldumpslow [ OPTS... ] [ LOGS... ]

Parse and summarize the MySQL slow query log. Options are

  --verbose    verbose
  --debug      debug
  --help       write this text to standard output

  -v           展示更详细的信息
  -d           debug
  -s ORDER     以哪种方式排序，默认at
                al: 平均锁定时间
                ar: 平均返回记录数
                at: 平均查询时间
                 c: 访问计数
                 l: 锁定时间
                 r: 返回记录
                 t: 查询时间
  -r           将-s的排序倒序
  -t NUM       top n的意思，展示最前面的几条
  -a           不去将数字展示成N，将字符串展示成'S'
  -n NUM       abstract numbers with at least n digits within names
  -g PATTERN   后边可以写一个正则，只有符合正则的行会展示
  -h HOSTNAME  慢查询日志以 主机名-slow.log的格式命名，-h可指定读取指定主机名的慢查询日志，默认情况下是*，读取所有的慢查询日志
  -i NAME      MySQL Server的实例名称（如果使用了mysql.server startup脚本的话）
  -l           不将锁定时间从总时间中减去

SHOW PROFILE [type [, type] ... ]
    [FOR QUERY n]
    [LIMIT row_count [OFFSET offset]]

type: {
    ALL                     显示所有信息
  | BLOCK IO                显示阻塞的输入输出次数
  | CONTEXT SWITCHES显示自愿及非自愿的上下文切换次数
  | CPU显示用户与系统CPU使用时间
  | IPC显示消息发送与接收的次数
  | MEMORY显示内存相关的开销，目前未实现此功能
  | PAGE FAULTS显示页错误相关开销信息
  | SOURCE列出相应操作对应的函数名及其在源码中的位置(行)
  | SWAPS显示swap交换次数
}

-- 默认展示15条
show profiles

-- 使用profiling_history_size调整展示的条目数
set profiling_history_size = 100;

mysql> SHOW PROFILES;
+----------+----------+--------------------------+
| Query_ID | Duration | Query                    |
+----------+----------+--------------------------+
|        0 | 0.000088 | SET PROFILING = 1        |
|        1 | 0.000136 | DROP TABLE IF EXISTS t1  |
|        2 | 0.011947 | CREATE TABLE t1 (id INT) |
+----------+----------+--------------------------+
3 rows in set (0.00 sec)

mysql> SHOW PROFILE;
+----------------------+----------+
| Status               | Duration |
+----------------------+----------+
| checking permissions | 0.000040 |
| creating table       | 0.000056 |
| After create         | 0.011363 |
| query end            | 0.000375 |
| freeing items        | 0.000089 |
| logging slow query   | 0.000019 |
| cleaning up          | 0.000005 |
+----------------------+----------+
7 rows in set (0.00 sec)

-- 默认情况下，只展示Status和Duration两列，如果想展示更多信息，可指定type。
mysql> SHOW PROFILE FOR QUERY 1;
+--------------------+----------+
| Status             | Duration |
+--------------------+----------+
| query end          | 0.000107 |
| freeing items      | 0.000008 |
| logging slow query | 0.000015 |
| cleaning up        | 0.000006 |
+--------------------+----------+
4 rows in set (0.00 sec)

-- 展示CPU相关的开销
mysql> SHOW PROFILE CPU FOR QUERY 2;
+----------------------+----------+----------+------------+
| Status               | Duration | CPU_user | CPU_system |
+----------------------+----------+----------+------------+
| checking permissions | 0.000040 | 0.000038 |   0.000002 |
| creating table       | 0.000056 | 0.000028 |   0.000028 |
| After create         | 0.011363 | 0.000217 |   0.001571 |
| query end            | 0.000375 | 0.000013 |   0.000028 |
| freeing items        | 0.000089 | 0.000010 |   0.000014 |
| logging slow query   | 0.000019 | 0.000009 |   0.000010 |
| cleaning up          | 0.000005 | 0.000003 |   0.000002 |
+----------------------+----------+----------+------------+
7 rows in set (0.00 sec)

-- 按照客户端IP分组，看哪个客户端的连接数最多
select client_ip, count(client_ip) as client_num
from (select substring_index(host, ':', 1) as client_ip
      from `information_schema`.processlist) as connect_info
group by client_ip
order by client_num desc;

-- 查看正在执行的线程，并按 Time 倒排序，看看有没有执行时间特别长的线程
select *
from `information_schema`.processlist
where Command != 'Sleep'
order by Time desc;

-- 找出所有执行时间超过 5 分钟的线程，拼凑出 kill 语句，方便后面查杀
select concat('kill ', id, ';')
from `information_schema`.processlist
where Command != 'Sleep'
  and Time > 300
order by Time desc;