Sergey Vojtovich 380069c235 MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH ... trx_sys_t::rw_trx_set is implemented as std::set, which does a few quite expensive operations under trx_sys_t::mutex protection: e.g. malloc/free when adding/removing elements. Traversing b-tree is not that cheap either. This has negative scalability impact, which is especially visible when running oltp_update_index.lua benchmark on a ramdisk. To reduce trx_sys_t::mutex contention std::set is replaced with LF_HASH. None of LF_HASH operations require trx_sys_t::mutex (nor any other global mutex) protection. Another interesting issue observed with std::set is reproducible ~2% performance decline after benchmark is ran for ~60 seconds. With LF_HASH results are stable. All in all this patch optimises away one of three trx_sys->mutex locks per oltp_update_index.lua query. The other two critical sections became smaller. Relevant clean-ups: Replaced rw_trx_set iteration at startup with local set. The latter is needed because values inserted to rw_trx_list must be ordered by trx->id. Removed redundant conditions from trx_reference(): it is (and even was) never called with transactions that have trx->state == TRX_STATE_COMMITTED_IN_MEMORY. do_ref_count doesn't (and probably even didn't) make any sense: now it is called only when reference counter increment is actually requested. Moved condition out of mutex in trx_erase_lists(). trx_rw_is_active(), trx_rw_is_active_low() and trx_get_rw_trx_by_id() were greatly simplified and replaced by appropriate trx_rw_hash_t methods. Compared to rw_trx_set, rw_trx_hash holds transactions only in PREPARED or ACTIVE states. Transactions in COMMITTED state were required to be found at InnoDB startup only. They are now looked up in the local set. Removed unused trx_assert_recovered(). Removed unused innobase_get_trx() declaration. Removed rather semantically incorrect trx_sys_rw_trx_add(). Moved information printout from trx_sys_init_at_db_start() to trx_lists_init_at_db_start().		2018-01-11 12:30:53 +04:00
..
sync0arr.cc	fix data races in rwlock	2017-12-19 13:03:04 +04:00
sync0debug.cc	MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH	2018-01-11 12:30:53 +04:00
sync0rw.cc	fix data races in rwlock	2017-12-19 13:03:04 +04:00
sync0sync.cc	MDEV-14638 - Replace trx_sys_t::rw_trx_set with LF_HASH	2018-01-11 12:30:53 +04:00