MDEV-23379 Deprecate&ignore InnoDB concurrency throttling parameters

The parameters innodb_thread_concurrency and innodb_commit_concurrency
were useful years ago when both computing resources and the implementation
of some shared data structures were limited. MySQL 5.0 or 5.1 had trouble
scaling beyond 8 concurrent connections. Most of the scalability bottlenecks
have been removed since then, and the transactions per second delivered
by MariaDB Server 10.5 should not dramatically drop upon exceeding the
'optimal' number of connections.

Hence, enabling any concurrency throttling for InnoDB actually makes
things worse. We have seen many customers mistakenly setting this to a
small value like 16 or 64 and then complaining the server was slow.

Ignoring the parameters allows us to remove some normally unused code
and data structures, which could slightly improve performance.

innodb_thread_concurrency, innodb_commit_concurrency,
innodb_replication_delay, innodb_concurrency_tickets,
innodb_thread_sleep_delay, innodb_adaptive_max_sleep_delay:
Deprecate and ignore; hard-wire to 0.

The column INFORMATION_SCHEMA.INNODB_TRX.trx_concurrency_tickets
will always report 0.

1 files changed, 0 insertions, 2 deletions

diff --git a/storage/innobase/trx/trx0i_s.cc b/storage/innobase/trx/trx0i_s.cc
index 8e46057f654..2736dbd285f 100644
--- a/storage/innobase/trx/trx0i_s.cc
+++ b/storage/innobase/trx/trx0i_s.cc
@@ -499,8 +499,6 @@ thd_done:
 
 	row->trx_rows_modified = trx->undo_no;
 
-	row->trx_concurrency_tickets = trx->n_tickets_to_enter_innodb;
-
 	row->trx_isolation_level = trx->isolation_level;
 
 	row->trx_unique_checks = (ibool) trx->check_unique_secondary;