所谓的read-ahead就是innodb根据你现在访问的数据,推测出你接下来可能要访问的数据,并把它们(可能要访问的数据)读入 内存。 二、read-ahead是怎么做到的: 1、总的来说read-ahead利用的是程序的局部性原理;在innodb的数据文件中是用页面来管理的,而每64个页面组成一个Extend 如果一个Extend的大多数据页面都
其中一个MySQL status变量就是Innodb_buffer_pool_read_ahead_evicted。它表示缓存池预读请求中被强制退出的数据页数量。如果MySQL服务器的数据页的访问频率很高,那么InnoDB会尝试进行页面预读,以提高性能。但是如果数据库中的页面频繁地更改,那么在页面更新时,预读会被强制退出。此变量用于记录被取消的预读页面的数量。
The SHOW ENGINE INNODB STATUS statement displays statistics to help you evaluate the effectiveness of the read-ahead algorithm. Statistics include counter information for the following global status variables: Innodb_buffer_pool_read_ahead Innodb_buffer_pool_read_ahead_evicted Innodb_buffer_pool_read...
InnoDB 使用2种预读算法来改善性能。 线性预读 是一种技术预测什么页面可能被马上需要基于在buffer 中的pages 被顺序访问。 你控制 当InnoDB 执行一个预读操作通过调整顺序page 访问的数目来触发异步请求, 使用配置参数 innodb_read_ahead_threshold。 在这个参数增加前,InnoDB 只会计算是否执行一个异步预取请求对于整个...
Innodb_buffer_pool_read_ahead Innodb_buffer_pool_read_ahead_evicted Innodb_buffer_pool_read_ahead_rnd This information can be useful when fine-tuning thesetting. Section 10.5.8, “Optimizing InnoDB Disk I/O”andSection 10.12.1, “Optimizing Disk I/O”....
A read-ahead request is an I/O request to prefetch multiple pages in the buffer pool asynchronously, in anticipation of impending need for these pages. The requests bring in all the pages in one extent. InnoDB uses two read-ahead algorithms to improve I/O performance: ...
A read-ahead request is an I/O request to prefetch multiple pages in the buffer pool asynchronously, in anticipation of impending need for these pages. The requests bring in all the pages in one extent. InnoDB uses two read-ahead algorithms to improve I/O performance: ...
The SHOW ENGINE INNODB STATUS command displays statistics to help you evaluate the effectiveness of the read-ahead algorithm. Statistics include counter information for the following global status variables: Innodb_buffer_pool_read_ahead Innodb_buffer_pool_read_ahead_evicted Innodb_buffer_pool_read_...
Innodb_buffer_pool_read_ahead_rnd This information can be useful when fine-tuning theinnodb_random_read_aheadsetting. For more information about I/O performance, seeSection 10.5.8, “Optimizing InnoDB Disk I/O”andSection 10.12.1, “Optimizing Disk I/O”....