Here are the screenshots comparing 10.5+ sawtooth pattern vs 10.4 and older versions.
Is there a bug fix for this or a configuration change available to restore the old behaviour where everything gets flushed continuously and switches up a gear when the hwm is reached?
There are couple of issues (from which some other are related): innodb_max_dirty_pages_pct_lwm=0 lost its special meaning https://jira.mariadb.org/browse/MDEV-24537 Adaptive flushing is still not getting invoked in 10.5.11 https://jira.mariadb.org/browse/MDEV-26055 No background flushing until innodb_adaptive_flushing_lwm is reached https://jira.mariadb.org/browse/MDEV-27942 You can try the: SET GLOBAL innodb_max_dirty_pages_pct_lwm=0.0001; suggestion to see if it works for you but for my workload (write heavy) it didn't help and the performance was still abysmal with stalls so I'm still holding on the 10.4 -> 10.5/10.6 upgrade (https://jira.mariadb.org/browse/MDEV-30501) rr