WL#9630: Change innodb_max_dirty_pages_pct_lwm default to 10
Affects: Server-8.0 — Status: Complete — Priority: Medium
In MySQL 8.0, we would like to change the default of innodb_max_dirty_pages_pct_lwm to 10. This is the default we are currently using in OPC MySQL, and should result in more stable throughput. We should also expect the default configuration to have larger buffer pools and thus benefit more from pre-flushing enabled. ** Upgrade Story ** With innodb_max_dirty_pages_pct_lwm=10, InnoDB will increase its flushing activity when >10% of the buffer pool contains modified ('dirty') pages. The motivation for this default change is to trade off peak throughput slightly, in exchange for more consistent performance. We do not expect the majority of users to see impact from this change, but symptomatically query throughput may be reduced after a number of sustained modifications. Users who wish to revert to the previous behavior can set innodb_max_dirty_pages_pct_lwm=0. The value of zero disables the increased flushing heuristic.
FR-1) The compiled default value of innodb_max_dirty_pages_pct_lwm changed from 0 to 10. NFR-1) Any changes required to MTR tests.
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