Hi, Sergey! On Jan 31, Sergey Vojtovich wrote: > At lp:maria/10.0 > > ------------------------------------------------------------ > revno: 3967 > revision-id: [email protected] > parent: [email protected] > committer: Sergey Vojtovich <[email protected]> > branch nick: 10.0 > timestamp: Fri 2014-01-31 18:19:43 +0400 > message: > MDEV-5597 - Reduce usage of LOCK_open: LOCK_flush > > Replaced LOCK_flush with per-share conditional variable. > === modified file 'sql/table_cache.cc' > --- a/sql/table_cache.cc 2014-01-30 12:49:05 +0000 > +++ b/sql/table_cache.cc 2014-01-31 14:19:43 +0000 > @@ -945,6 +949,7 @@ bool tdc_remove_table(THD *thd, enum_tdc > if ((share= tdc_delete_share(db, table_name))) > { > I_P_List <TABLE, TABLE_share> purge_tables; > + uint my_refs= 1; > > mysql_mutex_lock(&LOCK_open); > /* > @@ -969,28 +974,48 @@ bool tdc_remove_table(THD *thd, enum_tdc > if (kill_delayed_threads) > kill_delayed_threads_for_table(share); > > -#ifndef DBUG_OFF > - if (remove_type == TDC_RT_REMOVE_NOT_OWN) > + if (remove_type == TDC_RT_REMOVE_NOT_OWN || > + remove_type == TDC_RT_REMOVE_NOT_OWN_KEEP_SHARE) > { > TABLE_SHARE::All_share_tables_list::Iterator it(share->tdc.all_tables); > while ((table= it++)) > + { > + my_refs++; > DBUG_ASSERT(table->in_use == thd); > + } > } > -#endif > - > - mysql_rwlock_rdlock(&LOCK_flush); > + DBUG_ASSERT(share->tdc.all_tables.is_empty() || remove_type != > TDC_RT_REMOVE_ALL); > mysql_mutex_unlock(&LOCK_open); > > while ((table= purge_tables.pop_front())) > intern_close_table(table); > - mysql_rwlock_unlock(&LOCK_flush); > > - DBUG_ASSERT(share->tdc.all_tables.is_empty() || remove_type != > TDC_RT_REMOVE_ALL); > - tdc_release_share(share); > + if (remove_type != TDC_RT_REMOVE_UNUSED) > + { > + /* > + Even though current thread holds exclusive metadata lock on this > share > + (asserted above), concurrent FLUSH TABLES threads may be in process > of > + closing unused table instances belonging to this share. E.g.: > + thr1 (FLUSH TABLES): table= share->tdc.free_tables.pop_front(); > + thr1 (FLUSH TABLES): share->tdc.all_tables.remove(table); > + thr2 (ALTER TABLE): tdc_remove_table(); > + thr1 (FLUSH TABLES): intern_close_table(table); > + > + Current remove type assumes that all table instances (except for > those > + that are owned by current thread) must be closed before > + thd_remove_table() returns. Wait for such tables here. > + > + Unfortunately TABLE_SHARE::wait_for_old_version() cannot be used here > + because it waits for all table instances, whereas we have to wait > only > + for those that are not owned by current thread. > + */ > + mysql_mutex_lock(&share->tdc.LOCK_table_share); > + while (share->tdc.ref_count > my_refs) > + mysql_cond_wait(&share->tdc.COND_release, > &share->tdc.LOCK_table_share); > + mysql_mutex_unlock(&share->tdc.LOCK_table_share);
I'm sorry, I don't understand that at all. Why my_refs is only incremented in debug builds? In non-debug builds you wait until all tables but one are closed, in debug builds you may keep more than one table opened. You wait here on a condition, how do you know there's FLUSH TABLES (or anything at all) running that will signal this condition? > + } > > - /* Wait for concurrent threads to free unused objects. */ > - mysql_rwlock_wrlock(&LOCK_flush); > - mysql_rwlock_unlock(&LOCK_flush); > + tdc_release_share(share); > > found= true; > } Regards, Sergei _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
