如果新 innodb_buffer_pool_chunk_size值 * innodb_buffer_pool_instances 大于缓冲池初始化时的当前缓冲池大小， innodb_buffer_pool_chunk_size 则被截断为 innodb_buffer_pool_size/ innodb_buffer_pool_instances。

例如，如果缓冲池初始化为大小为2GB（2147483648 字节）、 4缓冲池实例和块大小为1GB（1073741824 字节），则块大小将被截断为等于 innodb_buffer_pool_size/ 的值innodb_buffer_pool_instances，如下所示：

$> mysqld --innodb-buffer-pool-size=2147483648 --innodb-buffer-pool-instances=4
--innodb-buffer-pool-chunk-size=1073741824;

mysql> SELECT @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
|                2147483648 |
+---------------------------+

mysql> SELECT @@innodb_buffer_pool_instances;
+--------------------------------+
| @@innodb_buffer_pool_instances |
+--------------------------------+
|                              4 |
+--------------------------------+

# Chunk size was set to 1GB (1073741824 bytes) on startup but was
# truncated to innodb_buffer_pool_size / innodb_buffer_pool_instances

mysql> SELECT @@innodb_buffer_pool_chunk_size;
+---------------------------------+
| @@innodb_buffer_pool_chunk_size |
+---------------------------------+
|                       536870912 |
+---------------------------------+

缓冲池大小必须始终等于 innodb_buffer_pool_chunk_size * 或它的倍数innodb_buffer_pool_instances。如果您更改 innodb_buffer_pool_chunk_size, innodb_buffer_pool_size 将自动调整为等于 innodb_buffer_pool_chunk_size * 或它的倍数的值innodb_buffer_pool_instances。调整发生在缓冲池初始化时。以下示例演示了此行为：

# The buffer pool has a default size of 128MB (134217728 bytes)

mysql> SELECT @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
|                 134217728 |
+---------------------------+

# The chunk size is also 128MB (134217728 bytes)

mysql> SELECT @@innodb_buffer_pool_chunk_size;
+---------------------------------+
| @@innodb_buffer_pool_chunk_size |
+---------------------------------+
|                       134217728 |
+---------------------------------+

# There is a single buffer pool instance

mysql> SELECT @@innodb_buffer_pool_instances;
+--------------------------------+
| @@innodb_buffer_pool_instances |
+--------------------------------+
|                              1 |
+--------------------------------+

# Chunk size is decreased by 1MB (1048576 bytes) at startup
# (134217728 - 1048576 = 133169152):

$> mysqld --innodb-buffer-pool-chunk-size=133169152

mysql> SELECT @@innodb_buffer_pool_chunk_size;
+---------------------------------+
| @@innodb_buffer_pool_chunk_size |
+---------------------------------+
|                       133169152 |
+---------------------------------+

# Buffer pool size increases from 134217728 to 266338304
# Buffer pool size is automatically adjusted to a value that is equal to
# or a multiple of innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances

mysql> SELECT @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
|                 266338304 |
+---------------------------+

此示例演示了相同的行为，但具有多个缓冲池实例：

# The buffer pool has a default size of 2GB (2147483648 bytes)

mysql> SELECT @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
|                2147483648 |
+---------------------------+

# The chunk size is .5 GB (536870912 bytes)

mysql> SELECT @@innodb_buffer_pool_chunk_size;
+---------------------------------+
| @@innodb_buffer_pool_chunk_size |
+---------------------------------+
|                       536870912 |
+---------------------------------+

# There are 4 buffer pool instances

mysql> SELECT @@innodb_buffer_pool_instances;
+--------------------------------+
| @@innodb_buffer_pool_instances |
+--------------------------------+
|                              4 |
+--------------------------------+

# Chunk size is decreased by 1MB (1048576 bytes) at startup
# (536870912 - 1048576 = 535822336):

$> mysqld --innodb-buffer-pool-chunk-size=535822336

mysql> SELECT @@innodb_buffer_pool_chunk_size;
+---------------------------------+
| @@innodb_buffer_pool_chunk_size |
+---------------------------------+
|                       535822336 |
+---------------------------------+

# Buffer pool size increases from 2147483648 to 4286578688
# Buffer pool size is automatically adjusted to a value that is equal to
# or a multiple of innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances

mysql> SELECT @@innodb_buffer_pool_size;
+---------------------------+
| @@innodb_buffer_pool_size |
+---------------------------+
|                4286578688 |
+---------------------------+

更改时应小心 innodb_buffer_pool_chunk_size，因为更改此值会增加缓冲池的大小，如上例所示。在更改 之前 innodb_buffer_pool_chunk_size，计算对 的影响， innodb_buffer_pool_size 以确保生成的缓冲池大小是可以接受的。

添加页面chunks（块大小由 定义 innodb_buffer_pool_chunk_size）

转换哈希表、列表和指针以使用内存中的新地址

将新页面添加到空闲列表

对缓冲池进行碎片整理并撤回（释放）页面

删除页面chunks（块大小由定义 innodb_buffer_pool_chunk_size）

转换哈希表、列表和指针以使用内存中的新地址