Type:
Priority:
Resolution:
Fixed
Component/s:
None
tc_acquire_table and tc_release_table are critical sections of table cache. Among other things, they update TABLE_SHARE::tdc.used_tables:
used_tables list is not really necessary for table cache to operate properly. We can change it with all_tables list instead. tc_acquire_table and tc_release_table wont need to access all_tables list at all.
The cost is as following:
2 additional pointers per TABLE object
SHOW OPEN TABLES will have to iterate all_tables and skip objects with in_use == 0
same for TABLE_SHARE::visit_subgraph()
same for kill_delayed_threads_for_table()
A patch for this task has been tested (read-only single table OLTP, 4 CPU linux server) and shown ~30% lower LOCK_open wait time and ~20% higher tps.
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Task
Major
MDEV-5864 Reduce usage of LOCK_open: TABLE_SHARE::tdc.free_tables
Sergei, please review attached patch. Committed patch didn't reach mailing list for some reason.