Please make innodb_max_dirty_pages_pct dynamic to match upstream

Documentation for this variable https://mariadb.com/kb/en/library/xtradbinnodb-server-system-variables/#innodb_max_dirty_pages_pct shows that the setting is not dynamic.

The upstream setting for this variable has always been dynamic. See: https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html#sysvar_innodb_max_dirty_pages_pct

That is quite odd. Please consider making this setting dynamic too.

Reasoning:

• you change your mind over the amount of dirty pages you want to hold - restarting the server is always inconvenient on a production system
• you adjust the setting to a low value prior to shutting down a system as this keeps downtime (when you can't connect to the system) as low as possible. Having a MariaDB server take a long time to shutdown (as it's flushing dirty pages) and not being able to see what state it's in or how far it's progressing can be really frustrating.
• if you set the value to 0 (or close to 0) then you know when it gets there that a shutdown will be fast. That's also handy.

Given upstream already has this functionality please keep compatibility. I can't see any benefit of this value being static.