The issue is caused by 59a0236da4 commit.
The initial intention of the commit was to speed up
"mariabackup --prepare".
The call stack of binlog position reading is the following:
▾ trx_rseg_mem_restore
▾ trx_rseg_array_init
▾ trx_lists_init_at_db_start
▸ srv_start
Both trx_lists_init_at_db_start() and trx_rseg_mem_restore() contain
special cases for srv_operation == SRV_OPERATION_RESTORE condition, and
on this condition only rseg headers are read to parse binlog position.
Performance impact is not so big.
The solution is to revert 59a0236da4.
This is based on a prototype by
Thirunarayanan Balathandayuthapani <thiru@mariadb.com>.
Binlog and Galera write-set replication information was written into
TRX_SYS page on each commit. Instead of writing to the TRX_SYS during
normal operation, InnoDB can make use of rollback segment header pages,
which are already being written to during a commit.
The following list of fields in rollback segment header page are added:
TRX_RSEG_BINLOG_OFFSET
TRX_RSEG_BINLOG_NAME (NUL-terminated; empty name = not present)
TRX_RSEG_WSREP_XID_FORMAT (0=not present; 1=present)
TRX_RSEG_WSREP_XID_GTRID
TRX_RSEG_WSREP_XID_BQUAL
TRX_RSEG_WSREP_XID_DATA
trx_sys_t: Introduce the fields
recovered_binlog_filename, recovered_binlog_offset, recovered_wsrep_xid.
To facilitate upgrade from older mysql or mariaDB versions, we will read
the information in TRX_SYS page. It will be overridden by the
information that we find in rollback segment header pages.
Mariabackup --prepare will read the metadata from the rollback
segment header pages via trx_rseg_array_init(). It will still
not read any undo log pages or recover any transactions.
