… t values(33); ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction Here I tried to insert a value out of [21,30],but it came out my insert still be blocked. The SHOW ENGINE INNODB… mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 1216, 1 row lock(s) MySQL thread id 31929…
Post: InnoDB's gap locks
March 27, 2012 By 14 Comments
… point we suppose that only the record 25 is locked. Then, we try to insert another value on the second session: transaction2… troubleshoot gap locks? Is possible to detect those gap locks using SHOW ENGINE INNODB STATUS: —TRANSACTION 72C, ACTIVE 755 sec 4 lock struct(s… no need to create locks to prevent that from happening. 2- innodb_locks_unsafe_for_binlog = 1. Disables the gap locks except for foreign…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… locks is displayed. OS Wait is not exactly the same as “reservation” – before falling back to complex wait using sync_array Innodb tries… Innodb kernel and still has 400 tickets to use. Innodb tries to limit thread concurrency allowing only innodb_thread_concurrency threads to run inside Innodb…
Post: Choosing innodb_buffer_pool_size
November 3, 2007 By 38 Comments
… may have other settings to play with. Finally you can try locking MySQL in memory by using –memlock – just be careful as… important Innodb algorithms are finely tuned with consideration what is in memory and what is on disk, for example when Innodb tries to avoid holding latches while doing IO while there could be locks set while accessing pages in…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
… ? Not really – for example you could try to update the row which you just locked with SELECT FOR UPDATE but this row… is missing in Innodb locking.? In my oppinion few rather important peices missing in Locking implementation of Innodb are: Lock table Innodb can lock tables but it will still need to set row level locks which is…
Post: Internals of InnoDB mutexes
September 7, 2006 By 4 Comments
…’s look on InnoDB mutex (schematic for simplification): spin_loop: for (i=0; i< innodb_spin_locks;i++) if (mutex_try_lock()) return; // success // we…; innodb_spin_locks is configurable via system variable innodb_sync_spin_loops (default value is 20) There we have: 1. Spin-loop – InnoDB uses…
Post: kernel_mutex problem. Or double throughput with single variable
December 2, 2011 By 17 Comments
… 0.0000 seconds the semaphore: Mutex at 0x2b0ccc8 ‘&kernel_mutex’, lock var 1 waiters flag 0 –Thread 140370752542464 has waited at… experiment. With innodb_sync_spin_loops=100 the kernel_mutex is still the main point of contention, but InnoDB tries to prevent the… by kernel_mutex problem. Further direction I want to try to limit innodb_thread_concurrency and also bind mysqld to less CPUs…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
… let you to try it out. Q14: Are there any plans to fix Innodb so it unlocks (or never locks) the rows if… isolation level READ COMMITTED, then InnoDB normally does not lock the ‘gaps’, and it does not lock rows whose latest committed version does…’ (lots of threads waiting for semaphores in SHOW INNODB STATUS), you can try to disable thread throttling completely by setting the value…
Post: Understand InnoDB spin waits, win a Percona Live ticket
September 2, 2011 By Leave a Comment
… understand how InnoDB handles mutexes. It tries a two-step approach to getting a lock on a mutex. First, a thread tries to lock the… from SHOW INNODB STATUS. Here’s what it means. Mutex spin waits 5870888 is the number of times a thread tried to…. And now that you know a little bit more about InnoDB locking strategies and how it’s exposed in the status output…
Post: Innodb performance gotcha w Larger queries.
August 28, 2009 By 7 Comments
… parser or it is something nasty going on on Innodb level, so I tried running the test with MyISAM tables instead. The… see on top for update workload ! I asked Yasufumi, our Innodb code ninja to take a look what it could be…: do not lock gaps */ set_also_gap_locks = FALSE; } } The “REPLACE 1000 rows” SQL doesn’t have “SELECT” so, InnoDB scan all of…
