转载自 mysql语句性能开销检测profiling详解

之前我介绍过msyql查询优化explain检查命令的使用，explain主要是检查sql语句的基本性能，sql是否优秀，但不能查看具体的涉及硬件资源的开销，今天要介绍的这个profiling工具可以更细节的查看资源的开销，比较详细。

首先这款性能检查工具是针对每个session生效的，session结束了就要重要发起查询检测。

默认是关闭的，需要手动开启：

SET profiling = 1;

开启之后，发往mysql服务器的语句可以通过SHOW PROFILES显示出来，默认显示15条，最大设置为100，通过设置变量profiling_history_size实现，设置为0将会禁用profiling。

语法

SHOW PROFILE [type [, type] ... ]

    [FOR QUERY n]

    [LIMIT row_count [OFFSET offset]]

type:

    ALL

  | BLOCK IO

  | CONTEXT SWITCHES

  | CPU

  | IPC

  | MEMORY

  | PAGE FAULTS

  | SOURCE

  | SWAPS

  

关于type的定义英文也简单：

• ALL displays all information

  
  

• BLOCK IO displays counts for block input and output operations

  
  

• CONTEXT SWITCHES displays counts for voluntary and involuntary context switches

  
  

• CPU displays user and system CPU usage times

  
  

• IPC displays counts for messages sent and received

  
  

• MEMORY is not currently implemented

  
  

• PAGE FAULTS displays counts for major and minor page faults

  
  

• SOURCE displays the names of functions from the source code, together with the name and line number of the file in which the function occurs

  
  

• SWAPS displays swap counts

使用示例

查看有没有启用profiling

mysql> SELECT @@profiling;

+-------------+

| @@profiling |

+-------------+

|           0 |

+-------------+

1 row in set (0.00 sec)

开启profiling

mysql> SET profiling = 1;

Query OK, 0 rows affected (0.00 sec)

运行要分析的SQL语句

mysql> DROP TABLE IF EXISTS t1;

Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE TABLE T1 (id INT);

Query OK, 0 rows affected (0.01 sec)

检查所有抓取到的分析语句性能指标

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)

显示单个分析语句性能指标，指最近执行次数最多的那一条

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)

具体查看某条分析语句的性能

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)

你也可以查看CPU或者其他资源消耗信息

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)

其他使用方式

也可以通过查表的方式查看分析语句的性能，所有show能看到的都会记录在INFORMATION_SCHEMA表中，比如：

SELECT STATE, FORMAT(DURATION, 6) AS DURATION FROM INFORMATION_SCHEMA.PROFILING WHERE QUERY_ID = 2 ORDER BY SEQ;

SHOW与INFORMATION_SCHEMA对应关系表：

INFORMATION_SCHEMA Name	SHOW Name	Remarks
QUERY_ID	Query_ID
SEQ
STATE	Status
DURATION	Duration
CPU_USER	CPU_user
CPU_SYSTEM	CPU_system
CONTEXT_VOLUNTARY	Context_voluntary
CONTEXT_INVOLUNTARY	Context_involuntary
BLOCK_OPS_IN	Block_ops_in
BLOCK_OPS_OUT	Block_ops_out
MESSAGES_SENT	Messages_sent
MESSAGES_RECEIVED	Messages_received
PAGE_FAULTS_MAJOR	Page_faults_major
PAGE_FAULTS_MINOR	Page_faults_minor
SWAPS	Swaps
SOURCE_FUNCTION	Source_function
SOURCE_FILE	Source_file
SOURCE_LINE	Source_line

注意

INFORMATION_SCHEMA这个表的使用方式已经在mysql5.7.2已经标记废除了，在未来的版本将会彻底删除掉，SHOW的使用方式在未来的版本也会替代掉，替代使用方式为MySQL Performance Schema，具体的参考官网的使用：https://dev.mysql.com/doc/refman/5.7/en/performance-schema.html

以上profiling所有介绍翻译来源于官网，原版可以参考：https://dev.mysql.com/doc/refman/5.7/en/show-profile.html