NOTE
InnoDB Flushing
Writing dirty buffer-pool pages and redo state to durable storage under checkpoints and background pressure.
This is a historical learning note and may contain outdated or incomplete understanding.
InnoDB modifies pages in the buffer pool and records redo before dirty pages must reach their data files. Background flushing and checkpoints keep the gap between durable redo and data-page state bounded and free reusable buffer pages.
Flushing is driven by several pressures, including dirty-page volume, redo/checkpoint age, and buffer-pool demand. It is not correct to assume every transaction commit immediately writes all changed data pages; durability primarily depends on the configured redo/binlog persistence path.