MySQL 8.3 Release Notes
您可以离线或在线配置 InnoDB 缓冲池大小。该节描述的行为适用于这两种方法。有关在线配置缓冲池大小的更多信息，请参阅 在线配置 InnoDB 缓冲池大小。
当增加或减少 innodb_buffer_pool_size 时，操作将以块的形式执行。块大小由 innodb_buffer_pool_chunk_size 配置选项定义，默认值为 128M。有关更多信息，请参阅 配置 InnoDB 缓冲池块大小。
缓冲池大小必须始终等于或是 innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances 的倍数。如果您配置 innodb_buffer_pool_size 为不等于或不是 innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances 的倍数的值，那么缓冲池大小将自动调整为等于或是 innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances 的倍数。
在以下示例中，innodb_buffer_pool_size 设置为 8G，innodb_buffer_pool_instances 设置为 16。innodb_buffer_pool_chunk_size 是 128M，这是默认值。
8G 是一个有效的 innodb_buffer_pool_size 值，因为 8G 是 innodb_buffer_pool_instances=16 * innodb_buffer_pool_chunk_size=128M 的倍数，即 2G。
$> mysqld --innodb-buffer-pool-size=8G --innodb-buffer-pool-instances=16mysql> SELECT @@innodb_buffer_pool_size/1024/1024/1024;
+------------------------------------------+
| @@innodb_buffer_pool_size/1024/1024/1024 |
+------------------------------------------+
| 8.000000000000 |
+------------------------------------------+在这个示例中，innodb_buffer_pool_size 设置为 9G，innodb_buffer_pool_instances 设置为 16。innodb_buffer_pool_chunk_size 是 128M，这是默认值。在这种情况下，9G 不是 innodb_buffer_pool_instances=16 * innodb_buffer_pool_chunk_size=128M 的倍数，因此 innodb_buffer_pool_size 将被调整为 10G，这是 innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances 的倍数。
$> mysqld --innodb-buffer-pool-size=9G --innodb-buffer-pool-instances=16mysql> SELECT @@innodb_buffer_pool_size/1024/1024/1024;
+------------------------------------------+
| @@innodb_buffer_pool_size/1024/1024/1024 |
+------------------------------------------+
| 10.000000000000 |
+------------------------------------------+innodb_buffer_pool_chunk_size 可以以 1MB（1048576 字节）单位增加或减少，但只能在启动时、命令行字符串或 MySQL 配置文件中修改。
命令行：
$> mysqld --innodb-buffer-pool-chunk-size=134217728配置文件：
[mysqld]
innodb_buffer_pool_chunk_size=134217728在更改 innodb_buffer_pool_chunk_size 时，以下条件适用：
-
如果新的
innodb_buffer_pool_chunk_size值 *innodb_buffer_pool_instances大于当前缓冲池大小时，innodb_buffer_pool_chunk_size将被截断为innodb_buffer_pool_size/innodb_buffer_pool_instances。例如，如果缓冲池初始化大小为
2GB（2147483648 字节），缓冲池实例为4，块大小为1GB（1073741824 字节），则块大小将被截断为innodb_buffer_pool_size/innodb_buffer_pool_instances，如下所示：$> 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或是
innodb_buffer_pool_chunk_size*innodb_buffer_pool_instances的倍数。如果您更改innodb_buffer_pool_chunk_size，innodb_buffer_pool_size将自动调整为等于或是innodb_buffer_pool_chunk_size*innodb_buffer_pool_instances的倍数。该调整将在缓冲池初始化时发生。# 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 | +---------------------------+以下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 | +---------------------------+在更改
innodb_buffer_pool_chunk_size时，需要小心，因为更改该值可能会增加缓冲池的大小，如上面的示例所示。在更改innodb_buffer_pool_chunk_size之前，计算对innodb_buffer_pool_size的影响，以确保结果缓冲池大小是可接受的。
Note
为了避免潜在的性能问题，块数（innodb_buffer_pool_size / innodb_buffer_pool_chunk_size）不应超过 1000。
可以使用 SET 语句动态设置 innodb_buffer_pool_size 配置选项，从而允许在不重新启动服务器的情况下调整缓冲池大小。例如：
mysql> SET GLOBAL innodb_buffer_pool_size=402653184;
Note
缓冲池大小必须等于或是 innodb_buffer_pool_chunk_size * innodb_buffer_pool_instances 的倍数。更改这些变量设置需要重新启动服务器。
在调整缓冲池大小之前，需要完成活动事务和通过 InnoDB API 执行的操作。当启动调整操作时，新的事务和需要访问缓冲池的操作必须等待调整操作完成。唯一的例外是，允许并发访问缓冲池，以便在缓冲池大小减少时撤回页面。允许并发访问的缺点是可能会导致暂时性的页面短缺，而页面正在被撤回。
Note
嵌套事务可能在缓冲池调整大小操作开始后失败。
变量 Innodb_buffer_pool_resize_status 报告一个字符串值，指示缓冲池调整大小进度；例如：
mysql> SHOW STATUS WHERE Variable_name='InnoDB_buffer_pool_resize_status';
+----------------------------------+----------------------------------+
| Variable_name | Value |
+----------------------------------+----------------------------------+
| Innodb_buffer_pool_resize_status | Resizing also other hash tables. |
+----------------------------------+----------------------------------+您也可以使用 Innodb_buffer_pool_resize_status_code 和 Innodb_buffer_pool_resize_status_progress 状态变量来监控在线缓冲池调整大小操作，这些变量报告数字值，适合程序化监控。
状态变量 Innodb_buffer_pool_resize_status_code 报告在线缓冲池调整大小操作的阶段状态代码。状态代码包括：
-
0：没有调整大小操作正在进行
-
1：开始调整大小
-
2：禁用 AHI（自适应哈希索引）
-
3：撤回块
-
4：获取全局锁
-
5：调整池大小
-
6：调整哈希大小
-
7：调整大小失败
状态变量 Innodb_buffer_pool_resize_status_progress 报告每个阶段的进度百分比值。百分比值在每个缓冲池实例处理后更新。当状态（由 Innodb_buffer_pool_resize_status_code 报告）从一个状态更改为另一个状态时，百分比值将重置为 0。
以下查询返回一个字符串值，指示缓冲池调整大小进度，一个代码，指示当前操作阶段，以及当前阶段的进度百分比值：
SELECT variable_name, variable_value
FROM performance_schema.global_status
WHERE LOWER(variable_name) LIKE "innodb_buffer_pool_resize%";缓冲池调整大小进度也可以在服务器错误日志中查看。以下示例显示了在增加缓冲池大小时记录的日志：
[Note] InnoDB: Resizing buffer pool from 134217728 to 4294967296. (unit=134217728)
[Note] InnoDB: disabled adaptive hash index.
[Note] InnoDB: buffer pool 0 : 31 chunks (253952 blocks) was added.
[Note] InnoDB: buffer pool 0 : hash tables were resized.
[Note] InnoDB: Resized hash tables at lock_sys, adaptive hash index, dictionary.
[Note] InnoDB: completed to resize buffer pool from 134217728 to 4294967296.
[Note] InnoDB: re-enabled adaptive hash index.以下示例显示了在减少缓冲池大小时记录的日志：
[Note] InnoDB: Resizing buffer pool from 4294967296 to 134217728. (unit=134217728)
[Note] InnoDB: disabled adaptive hash index.
[Note] InnoDB: buffer pool 0 : start to withdraw the last 253952 blocks.
[Note] InnoDB: buffer pool 0 : withdrew 253952 blocks from free list. tried to relocate
0 pages. (253952/253952)
[Note] InnoDB: buffer pool 0 : withdrawn target 253952 blocks.
[Note] InnoDB: buffer pool 0 : 31 chunks (253952 blocks) was freed.
[Note] InnoDB: buffer pool 0 : hash tables were resized.
[Note] InnoDB: Resized hash tables at lock_sys, adaptive hash index, dictionary.
[Note] InnoDB: completed to resize buffer pool from 4294967296 to 134217728.
[Note] InnoDB: re-enabled adaptive hash index.使用 --log-error-verbosity=3 启动服务器时，会在错误日志中记录在线缓冲池调整大小操作的附加信息。附加信息包括 Innodb_buffer_pool_resize_status_code 报告的状态代码和 Innodb_buffer_pool_resize_status_progress 报告的百分比进度值。
[Note] [MY-012398] [InnoDB] Requested to resize buffer pool. (new size: 1073741824 bytes)
[Note] [MY-013954] [InnoDB] Status code 1: Resizing buffer pool from 134217728 to 1073741824
(unit=134217728).
[Note] [MY-013953] [InnoDB] Status code 1: 100% complete
[Note] [MY-013952] [InnoDB] Status code 1: Completed
[Note] [MY-013954] [InnoDB] Status code 2: Disabling adaptive hash index.
[Note] [MY-011885] [InnoDB] disabled adaptive hash index.
[Note] [MY-013953] [InnoDB] Status code 2: 100% complete
[Note] [MY-013952] [InnoDB] Status code 2: Completed
[Note] [MY-013954] [InnoDB] Status code 3: Withdrawing blocks to be shrunken.
[Note] [MY-013953] [InnoDB] Status code 3: 100% complete
[Note] [MY-013952] [InnoDB] Status code 3: Completed
[Note] [MY-013954] [InnoDB] Status code 4: Latching whole of buffer pool.
[Note] [MY-013953] [InnoDB] Status code 4: 14% complete
[Note] [MY-013953] [InnoDB] Status code 4: 28% complete
[Note] [MY-013953] [InnoDB] Status code 4: 42% complete
[Note] [MY-013953] [InnoDB] Status code 4: 57% complete
[Note] [MY-013953] [InnoDB] Status code 4: 71% complete
[Note] [MY-013953] [InnoDB] Status code 4: 85% complete
[Note] [MY-013953] [InnoDB] Status code 4: 100% complete
[Note] [MY-013952] [InnoDB] Status code 4: Completed
[Note] [MY-013954] [InnoDB] Status code 5: Starting pool resize
[Note] [MY-013954] [InnoDB] Status code 5: buffer pool 0 : resizing with chunks 1 to 8.
[Note] [MY-011891] [InnoDB] buffer pool 0 : 7 chunks (57339 blocks) were added.
[Note] [MY-013953] [InnoDB] Status code 5: 100% complete
[Note] [MY-013952] [InnoDB] Status code 5: Completed
[Note] [MY-013954] [InnoDB] Status code 6: Resizing hash tables.
[Note] [MY-011892] [InnoDB] buffer pool 0 : hash tables were resized.
[Note] [MY-013953] [InnoDB] Status code 6: 100% complete
[Note] [MY-013954] [InnoDB] Status code 6: Resizing also other hash tables.
[Note] [MY-011893] [InnoDB] Resized hash tables at lock_sys, adaptive hash index, dictionary.
[Note] [MY-011894] [InnoDB] Completed to resize buffer pool from 134217728 to 1073741824.
[Note] [MY-011895] [InnoDB] Re-enabled adaptive hash index.
[Note] [MY-013952] [InnoDB] Status code 6: Completed
[Note] [MY-013954] [InnoDB] Status code 0: Completed resizing buffer pool at 220826 6:25:46.
[Note] [MY-013953] [InnoDB] Status code 0: 100% complete调整大小操作由后台线程执行。当增加缓冲池大小时，调整大小操作：
-
以
块（块大小由innodb_buffer_pool_chunk_size定义）添加页面 -
将哈希表、列表和指针转换为使用新地址
-
将新页面添加到空闲列表
在这些操作进行时，其他线程被阻止访问缓冲池。
当减少缓冲池大小时，调整大小操作：
-
碎片整理缓冲池并撤回（释放）页面
-
以
块（块大小由innodb_buffer_pool_chunk_size定义）移除页面 -
将哈希表、列表和指针转换为使用新地址
在这些操作中，只有碎片整理缓冲池和撤回页面允许其他线程并发访问缓冲池。