【笔记】InnoDB内存分配_MySQL-Mysql Tutorial-php.cn

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【笔记】InnoDB内存分配_MySQL

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Jun 01, 2016 pm 01:06 PM

原文：http://www.mysqlperformanceblog.com/2006/05/30/innodb-memory-usage/

有很多问题是有关InnoDB如何分配内存的。这里我试图解释下启动时内存的分配情况。先列出重要的常量：

NBLOCKS=innoDB缓冲池的块数量= innodb_buffer_pool_size / 16384

OS_THREADS = if (innodb_buffer_pool_size >= 1000Mb) = 50000

else if (innodb_buffer_pool_size >= 8Mb) = 10000

else = 1000 (对于Linux这类系统是正确的，对于Windows则有另一个计算方式)

所以InnoDB使用的内存量：

l innodb缓冲池内存

l innodb额外内存池大小

l innodb记录缓冲大小

l 自适应哈希索引, 大小= innodb缓冲池 / 64

l 系统目录哈希, 大小 = 6 * innodb缓冲池 / 512

l 同步数组（sync_array）使用的内存,为同步单元利用，大小 = OS_THREADS * 152

l 系统事件（os_events）的内存, 也为同步单元利用，大小= OS_THREADS * 216

l 系统锁定的内存, 大小=5 * 4 * NBLOCKS

所以，最后的innodb的公式：

缓冲池大小+缓冲记录大小+额外内存池大小+ 812 / 16384 * 缓冲池大小 + OS_THREADS * 368
为简单起见：812 / 16384 * 缓冲池大小 ~~ 缓冲池大小/ 20

和 OS_THREADS*368 = 17.5MB 如果缓冲池大小> 1000MB

= 3.5MB 如果缓冲池大小> 8MB

举个例子，比如你的缓冲池大小=1500M，额外内存池大小=20M，记录缓冲大小=8M，那么InnoDB分配的内存= 1500M + 20M + 8M + 1500/20M + 17.5M = 1620.5M.

在你计划利用你的服务器内存时，你要考虑到额外内存的利用。

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