Until PHP 5.6, write() is called regardless of whether anything changed. We should detect changes and no-op if there's nothing to do. This is useful for multi-DC sessions to cut writes down to a trickle (nearly all in the hot DC).
Related Gerrit Patches:
|mediawiki/core : master||Avoiding writing sessions for no reason|
|Open||aaron||T88445 MediaWiki active/active datacenter investigation and work (tracking)|
|Resolved||aaron||T88635 ObjectCacheSessionHandler should avoid pointless writes in write()|