profiling分析

mysql默认关闭

mysql> show variables like '%profiling%';

mysql> show variables like '%profiling%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| have_profiling         | YES   |
| profiling              | OFF   |
| profiling_history_size | 15    |
+------------------------+-------+

开启profiling

mysql> set profiling=on;

mysql> show variables like '%profiling%';
+------------------------+-------+
| Variable_name          | Value |
+------------------------+-------+
| have_profiling         | YES   |
| profiling              | ON    |
| profiling_history_size | 15    |
+------------------------+-------+

查看profiles

mysql> show profiles;

mysql> show profiles;
+----------+------------+-----------------------------------+
| Query_ID | Duration   | Query                             |
+----------+------------+-----------------------------------+
|        1 | 0.00232350 | show variables like '%profiling%' |
|        2 | 0.00013675 | SELECT DATABASE()                 |
|        3 | 0.00061925 | show databases                    |
|        4 | 0.00015050 | show tables                       |
|        5 | 0.00031075 | show tables                       |
|        6 | 0.00031950 | select * from tb_bk_order         |
+----------+------------+-----------------------------------+

查看sql cpu和io开销

mysql> show profile cpu ,block io for query 6;

mysql> show profile cpu ,block io for query 6;
+----------------------+----------+----------+------------+--------------+---------------+
| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting             | 0.000084 | 0.000040 |   0.000042 |            0 |             0 |
| checking permissions | 0.000013 | 0.000005 |   0.000005 |            0 |             0 |
| Opening tables       | 0.000016 | 0.000007 |   0.000008 |            0 |             0 |
| init                 | 0.000030 | 0.000015 |   0.000015 |            0 |             0 |
| System lock          | 0.000009 | 0.000005 |   0.000005 |            0 |             0 |
| optimizing           | 0.000006 | 0.000002 |   0.000003 |            0 |             0 |
| statistics           | 0.000011 | 0.000006 |   0.000005 |            0 |             0 |
| preparing            | 0.000010 | 0.000005 |   0.000006 |            0 |             0 |
| executing            | 0.000004 | 0.000001 |   0.000001 |            0 |             0 |
| Sending data         | 0.000092 | 0.000046 |   0.000048 |            0 |             0 |
| end                  | 0.000007 | 0.000003 |   0.000003 |            0 |             0 |
| query end            | 0.000007 | 0.000003 |   0.000004 |            0 |             0 |
| closing tables       | 0.000007 | 0.000004 |   0.000003 |            0 |             0 |
| freeing items        | 0.000013 | 0.000006 |   0.000007 |            0 |             0 |
| cleaning up          | 0.000011 | 0.000006 |   0.000006 |            0 |             0 |
+----------------------+----------+----------+------------+--------------+---------------+

其它性能指标:

all            -- 显示所有的开销信息

block io   -- 显示块io相关的开销

context switches    --上下文切换相关的开销

cpu    -- 显示cpu相关的开销

ipc     -- 显示发送和接收相关的开销

memory   -- 显示内存相关的开销

page faults  --显示页面错误相关的开销

source  -- 显示和source_function, source_file, source_line相关的开销信息

swaps   -- 显示交换次数相关的开销.

Status中如果出现以下指标,需要优化:

converting HEAP to MyISAM 查询结果太大,内存不够用往磁盘上搬

creating tmp table  创建临时表,拷贝数据到临时表,用完再删除临时表

coping to tmp table on disk 把内存中的临时表复制到磁盘, 危险!

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