MySQL5.7 線上調整Innodb_Buffer_Pool_size不用重啟mysql進程

MySQL5.7 線上調整Innodb_Buffer_Pool_size不用重啟mysql進程

在之前的版本，調整Innodb_Buffer_Pool_size大小必須重啟mysql進程才可以生效，如今在MySQL5.7裡，可以直接動態設定，方便了很多。

這個功能應用的情境：
一、機器增加記憶體，DBA粗心大意忘記調大Innodb_Buffer_Pool_size了
二、工作交接，新來的DBA發現前任DBA設定的Innodb_Buffer_Pool_size不合理

需要注意的地方，在調整Buffer_Pool期間，使用者的請求將會阻塞，直到調整完畢，所以請勿在白天調整，在淩晨3-4點低峰期調整。

調整時，內部把資料頁移動到一個新的位置，單位是塊。如果想增加移動的速度，需要調整innodb_buffer_pool_chunk_size參數的大小，預設是128M。

例（把BP 128M增大為384M）：

mysql> SELECT @@innodb_buffer_pool_size;

+---------------------------+

| @@innodb_buffer_pool_size |

+---------------------------+

|                134217728 |

+---------------------------+

1 row in set (0.00 sec)

mysql> SELECT @@innodb_buffer_pool_chunk_size;

+---------------------------------+

| @@innodb_buffer_pool_chunk_size |

+---------------------------------+

|                      134217728 |

+---------------------------------+

1 row in set (0.00 sec)

mysql> SET GLOBAL innodb_buffer_pool_size=402653184;

Query OK, 0 rows affected (0.01 sec)

mysql> SELECT @@innodb_buffer_pool_size;

+---------------------------+

| @@innodb_buffer_pool_size |

+---------------------------+

|                402653184 |

+---------------------------+

1 row in set (0.00 sec)

innodb_buffer_pool_chunk_size的大小，計算公式是innodb_buffer_pool_size / innodb_buffer_pool_instances

比如現在初始化innodb_buffer_pool_size為2G，innodb_buffer_pool_instances執行個體為4，innodb_buffer_pool_chunk_size設定為1G，那麼會自動把innodb_buffer_pool_chunk_size 1G調整為512M，例：
./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 |

+---------------------------+

1 row in set (0.00 sec)

 

mysql> SELECT @@innodb_buffer_pool_instances;

+--------------------------------+

| @@innodb_buffer_pool_instances |

+--------------------------------+

|                              4 |

+--------------------------------+

1 row in set (0.00 sec)

 

# 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 |

+---------------------------------+

1 row in set (0.00 sec)

監控Buffer Pool調整進程

mysql> SHOW STATUS WHERE Variable_name='InnoDB_buffer_pool_resize_status';

+----------------------------------+----------------------------------+

| Variable_name                    | Value                            |

+----------------------------------+----------------------------------+

| Innodb_buffer_pool_resize_status | Resizing also other hash tables. |

+----------------------------------+----------------------------------+

1 row in set (0.00 sec)

查看錯誤記錄檔：
（增大）

[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.

（減少）

[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.

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