Understanding the lock manager internals with the fb lock print utility
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The document provides an overview of the fb_lock_print utility and the lock manager in Firebird, covering the types of locks, their usage, and features such as deadlock detection and monitoring. It discusses internal vs external locks, different lock types and states, and tuning options for the lock manager. Additionally, it includes details on configuring the lock manager and using the lock print utility for monitoring and output control.
Understanding the lock manager internals with the fb lock print utility
- 1. Understanding the lock manager with the fb_lock_print utility Dmitry Yemanov mailto:dimitr@firebirdsql.org Firebird Project http://www.firebirdsql.org/
- 2. Synchronization in Firebird Internal vs external locks Mutexes, spinlocks, RW locks, latches
- 3. Lock manager Features of the global locks Multiple states (SR, PR, SW, PW, EX)
- 7. Lock Types and their Usage Lock types Database lock
- 8. Existence locks (table, procedure, index, collation)
- 11. Sweep, shadow, monitoring, etc locks Page locks (!)
- 12. Lock Types and their Usage Lock types LCK_database = 1 // Root of lock tree LCK_relation = 2 // Individual relation lock LCK_bdb = 3 // Individual buffer block LCK_tra = 4 // Individual transaction lock LCK_rel_exist = 5 // Relation existence lock LCK_idx_exist = 6 // Index existence lock LCK_attachment = 7 // Attachment lock ...
- 13. Locks and Firebird Architectures SuperServer No page locks
- 14. Small lock table
- 15. Fast LM operations Classic and SuperClassic Page locks are widely used
- 16. Large lock table
- 17. LM operations may require IPC
- 18. Lock Manager in Classic IPC IPC IPC Connection 1 Connection 2 fb_inet_server fb_inet_server fb_lock_mgr Lock table (shmem)
- 19. Inside the Lock Table Block types Header section
- 20. Lock owners
- 21. Lock resources
- 22. Lock requests Internals Single mutex around the shmem region
- 23. Remappings
- 24. Hash table of lock keys
- 25. Inside the Lock Table Lock resource Series: page lock Key: 01:75 State: PR Lock request 1 PR (granted) Lock request 3 EX (pending) Lock request 4 EX (pending) Owner 1 PID = 1008 Owner 3 PID = 870 Owner 4 PID = 114 Lock request 2 PR (granted) Owner 2 PID = 788
- 26. Inside the Lock Table Owner states Waiting = 0x4
- 27. Signaled = 0x10 Request states Pending = 0x2
- 28. Blocking = 0x1
- 29. Blocking seen = 0x100
- 30. Tuning the Lock Manager Configuration options LockMemSize (1MB) ~= <cache pages> * <max connections> * 100
- 31. LockSemCount (32) – deprecated in v2.5
- 32. LockHashSlots (1009) Other considerations FIREBIRD_LOCK envvar
- 33. Using the Lock Print Utility Output control switches -o [wners]
- 34. -l [ocks]
- 35. -r [equests]
- 37. -a [ll]
- 38. -w [ait list] Default output Header and owners only
- 39. Using the Lock Print Utility Interactive mode -i [aotw] <number> <number>
- 40. Acquires, operations, types, waits
- 41. Seconds and intervals Other options -c
- 42. -d <database> or -f <lock file>
- 43. -m
- 44. Questions?