mysql数据库参数innodb_buffer_pool_size和max_connections

接到报故,查看mysql数据库以下参数

1、innodb_buffer_pool_size

2、max_connections

 

该参数定义了数据缓冲区buffer pool大小,类似于oracle的db_cache_size

mysql> show global variables like 'innodb_buffer_pool_size';
+-------------------------+-----------+
| Variable_name           | Value     |
+-------------------------+-----------+
| innodb_buffer_pool_size | 134217728 |
+-------------------------+-----------+
1 row in set (0.00 sec)

那么如何设置该参数大小呢?首先查看运行时buffer pool相关数据指标:

mysql> show global status like 'Innodb_buffer_pool_pages_data';
+-------------------------------+-------+
| Variable_name                 | Value |
+-------------------------------+-------+
| Innodb_buffer_pool_pages_data | 314   |
+-------------------------------+-------+
1 row in set (0.00 sec)

mysql> show global status like 'Innodb_buffer_pool_pages_total';
+--------------------------------+-------+
| Variable_name                  | Value |
+--------------------------------+-------+
| Innodb_buffer_pool_pages_total | 8191  |
+--------------------------------+-------+
1 row in set (0.00 sec)

mysql> show global status like 'Innodb_page_size';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| Innodb_page_size | 16384 |
+------------------+-------+
1 row in set (0.00 sec)

上述三项指标的含义如下:

Innodb_buffer_pool_pages_data
The number of pages in the InnoDB buffer pool containing data. The number includes both dirty and
clean pages.

Innodb_buffer_pool_pages_total
The total size of the InnoDB buffer pool, in pages.

Innodb_page_size
InnoDB page size (default 16KB). Many values are counted in pages; the page size enables them to be
easily converted to bytes

计算Innodb_buffer_pool_pages_data/Innodb_buffer_pool_pages_total*100%
当结果 > 95% 则增加 innodb_buffer_pool_size, 建议使用物理内存的 75%
当结果 < 95% 则减少 innodb_buffer_pool_size, 
建议设置大小为: Innodb_buffer_pool_pages_data* Innodb_page_size * 1.05 / (1024*1024*1024)

--------------------------------------------------------------------------------------------------------------------------------------------------------

MySQL服务器的连接数并不是要达到最大的100%为好,还是要具体问题具体分析,下面就对MySQL服务器最大连接数的合理设置进行了详尽的分析,供您参考。

我们经常会遇见“MySQL: ERROR 1040: Too many connections”的情况,一种是访问量确实很高,MySQL服务器抗不住,这个时候就要考虑增加从服务器分散读压力,另外一种情况是MySQL配置文件中max_connections值过小:

mysql> show variables like 'max_connections';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| max_connections | 256 |
+-----------------+-------+

这台MySQL服务器最大连接数是256,然后查询一下服务器响应的最大连接数:

mysql> show global status like 'Max_used_connections';

MySQL服务器过去的最大连接数是245,没有达到服务器连接数上限256,应该没有出现1040错误,比较理想的设置是:

Max_used_connections / max_connections * 100% ≈ 85%

最大连接数占上限连接数的85%左右,如果发现比例在10%以下,MySQL服务器连接上线就设置得过高了。

posted @ 2016-10-07 14:12  paul_hch  阅读(9914)  评论(0编辑  收藏  举报