New Features
Thread Pool high priority scheduling is now enabled by default by changing the default thread_pool_high_prio_tickets value from 0 to 4294967295.
Percona Server now supports Low priority queue throttling. This feature should improve Thread Pool performance under high concurrency in a situation when thread groups are oversubscribed.
Introduced new thread_pool_high_prio_mode to provide more fine-grained control over high priority scheduling either globally or per connection in Thread Pool.
Percona Server has extended mysqlbinlog to provide SSL and compression support.
Percona Server has reduced the performance overhead of the User Statistics feature.
Bugs Fixed
INSTALL PLUGIN statement would crash server if User Statistics were enabled. Bug fixed #1011047.
innodb_log_checksum_algorithm did not have any effect when set from my.cnf or mysqld command line, it would have effect only if set dynamically. Bug fixed #1248505.
Server would crash on shutdown if Atomic write support for Fusion-io devices feature is enabled. Bug fixed #1255628 (Jan Lindström).
Percona Server would crash when data was select from XTRADB_RSEG table when InnoDB system table space was initialized with lower then default number of rollback segments. Bug fixed #1260259.
Certain types of workloads (large result sets, blobs, slow clients) can have longer waits on network I/O (socket reads and writes). Whenever server waits, this should be communicated to the Thread Pool, so it can start new query by either waking a waiting thread or sometimes creating a new one. Ported MariaDB patch MDEV-156, bug fixed #1159743.
mysqldump --innodb-optimize-keys was generating incorrect CREATE TABLE statements for partitioned tables. Bug fixed #1233841.
Fixed errors when server was compiled with -DWITH_LIBWRAP=ON option. Bug fixed #1240442.
If innobase_atomic_writes was used on separate undo files that do not exists would lead to operating system error. Bug fixed #1255638 (Jan Lindström).
Default value for thread_pool_max_threads has been changed from 500 to 100 000 (the maximum supported number of connections), because limiting the total number of threads in the Thread Pool can result in deadlocks and uneven distribution of worker threads between thread groups in case of stalled connections. Bug fixed #1258097.
PURGE CHANGED_PAGE_BITMAPS BEFORE statement would delete the changed page data after the specified LSN and up to the start of the next bitmap file. If this data were to be used for fast incremental backups, its absence would cause Percona XtraBackup to fall back to the full-scan incremental backup mode. Bug fixed #1260035 (Andrew Gaul).
Server performance could degrade under heavy load or it could deadlock on shutdown while performing purge. Bug fixed #1236696.
Server could crash under heavy load if InnoDB compression was used. Bug fixed #1240371.
Redo log checksum mismatches would be diagnosed using the data page checksum algorithm setting instead of redo log checksum algorithm one. Bug fixed #1250148.
Other bugs fixed: bug #1082333, bug #1260945, bug #1248046, bug #1243067, bug #1238563, bug #1258154 (upstream bug #71092), bug #1242748, bug #1239062, bug #1200788, bug #1193319, bug #1240044.
