1. MySQL 5.1 Configuration Files & Options Part II
Presented by: Sheeri K. Cabral
Twitter: @sheeri

2. About Pythian Recognized Leader: Expertise:
Global industry-leader in database infrastructure services for Oracle, Oracle Applications, MySQL and SQL Server
150 current multinational companies such as Forbes.com, Fox Sports and Western Union to help manage their complex IT deployments
Expertise:
One of the world’s largest concentrations of dedicated, full-time DBA expertise.
Global Reach & Scalability:
24/7/365 global remote support for DBA and consulting, systems administration, special projects or emergency response
- Successful growing business for more than 10 years
- Served many customers with complex requirements/infrastructure just like yours.
- Operate globally for 24 x 7 “always awake” services 2 2

3. INSERT DELAYED max_delayed_threads (20)
if 0, INSERT DELAYED is disabled
Delayed_insert_threads (0)
Delayed_writes (0), Delayed_errors (0)
Not_flushed_delayed_rows (0)
DELAYED keyword is ignored on InnoDB; basically just a way to get around table-level locking on MyISAM tables. This is not durable (“D” in ACID compliant)

4. INSERT DELAYED delayed_insert_limit (100) delayed_insert_timeout (300)
delayed_queue_size (1000)
max_insert_delayed_threads (20)
max_delayed_threads
Delayed_insert_threads
delayed_insert_limit: When doing a bulk insert from INSERT DELAYED, process any SELECTs after this many records have been inserted
delayed_insert_timeout: How long the handler waits for another INSERT DELAYED before terminating
delayed_queue_size: Per-table queue size for INSERT DELAYED. If this fills, an INSERT DELAYED statement will “hang”
max_delayed_threads: Max # of threads to handle INSERT DELAYED. If all threads are in use, further INSERT DELAYED statements ignore DELAYED. Thus, 0 disables DELAYED.
max_insert_delayed_threads – same as max_delayed_threads
Delayed_insert_threads: How many handler threads are in use

5. Timeouts back_log (50) net_read_timeout (30) net_retry_count (10)
net_write_timeout (60)
back_log=size of TCP listen queue, how many outstanding requests MySQL can have before it stops answering new requests
net_read_timeout, net_write_timeout – only for TCP connections
net_retry_count is for interrupted read connections.

6. More Timeouts connect_timeout (10) wait_timeout (28800)
interactive_timeout (28800)
Increasing the connect_timeout value might help if clients frequently encounter errors of the form Lost connection to MySQL server at 'XXX', system error: errno. If this is too low, Aborted_connects status variable will be higher (but is not the only reason)
wait_timeout is how long to wait before killing sleeping non-interactive timeouts.

7. Non-InnoDB Disk I/O flush (OFF)
Sync changes to disk after every SQL statement
If ON, write changes to disk; let OS handle sync
flush_time (0)
Close tables and sync data to disk every x seconds
0 = disabled
Enable for systems with very few resources

8. OS-Related Variables skip_external_locking (ON)
thread_handling (one-thread-per-connection)
Open_streams (0)
skip_external_locking: If 1, Do not use system locking; see – turn to 0 if you need to lock tables externally, as for myisamchk. “Note that if you use this option on a system on which lockd does not fully work (such as Linux), it is easy for mysqld to deadlock.”
thread_handling:
valid values: one-thread, one-thread-per-connection (useful for debugging linux, also the default)

9. Linux Parameters large_files_support (ON) Use files >2Gb
large_pages (OFF)
Use pages >4Kb
large_page_size
Size of memory pages if large pages are used

10. File Descriptors table_open_cache (8,128)
Independent of innodb_open_files
Open_tables (224)
Opened_tables (519)
if Opened_tables increases rapidly, the table_open_cache should be increased (if possible).

11. File Descriptor Usage Open_files (152) Opened_files (974,785)
open_files_limit (25,000)
open_files_limit can be set, but the server-reported value is the # of files the OS allows MySQL to open. If 0,. MySQL can't set this value.
Not really anything to optimize here, just knowledge of how many files have used a certain library call (my_open) to open a file.
Open_files shouldn't be close to open_files_limit, that isn't a problem here.

12. TCP/Networking skip_networking (OFF) max_allowed_packet (24M)
net_buffer_length
net_buffer_length = Per-client start buffer length, max_allowed_packet is max, shrinks down to net_buffer_length after each query

13. Locking Status Variables
Table_locks_immediate (52,016,680)
Table_locks_waited (4)
Com_lock_tables (0)
Com_unlock_tables (400)
Table_locks_immediate
# times a table lock request was granted immediately
Table_locks_waited
# times a table lock request had to wait (big # is a problem)
Com_lock_tables
Com_unlock_tables

14. Locking System Variables
sql_buffer_result (OFF)
low_priority_updates (OFF)
sql_low_priority_updates
max_write_lock_count (4,294,967,295)
sql_buffer_result (OFF)
If ON, forces results to be stored in temp tables, releases locks earlier than if not enabled. Session variable only. Useful for, say, if it takes a long time for a result to be sent to a client.
low_priority_updates (OFF) If on, writes are lower priority than reads for table-level locking tables. ie, MyISAM, not InnoDB. called sql_low_priority_updates before, both show up in SHOW GLOBAL VARIABLES currently.
max_write_lock_count (4,294,967,295)
After this many write locks, allow a read lock. Basically by default writes are higher priority than reads, but if you want x writes to happen, then allow a read, set this variable.

15. Storage Engines have_csv (YES) have_innodb (YES) have_ndbcluster (NO)
That's all, nothing for MyISAM, federated, archive, etc. CSV is used in system tables (general log, slow log) by default.

16. MyISAM-specific concurrent_insert (2) delay_key_write (ON)
keep_files_on_create (OFF)
ALSO - (sql_)low_priority_updates from slide 100
concurrent_insert. 1=default, concurrent_insert if no fragmentation. 2, concurrent_insert even with fragmentation. 0 = no concurrent insert.
delay_key_write ON=default, key buffer not flushed for tables created with DELAY_KEY_WRITE keyword. Other values = OFF and ALL, which treats all MyISAM tables as having DELAY_KEY_WRITE on.
keep_files_on_create = overwrite existing MYI and MYD files when a .frm file isn't present. Set to on or always explicitly use INDEX_DIRECTORY and DATA_DIRECTORY to not overwrite MYI and MYD files. If a .frm file is present, mysqld returns an error that the table exists.

17. MyISAM-specific myisam_data_pointer_size (6)
myisam_stats_method (nulls_unequal )
myisam_use_mmap (OFF)
myisam_data_pointer_size = The default pointer size in bytes, to be used by CREATE TABLE for MyISAM tables when no MAX_ROWS option is specified. This variable cannot be less than 2 or larger than 7. The default value is 6. A value of 4 allows tables up to 4GB; a value of 6 allows tables up to 256TB. If you get “Table is full” you may need to increase this, or set MAX_ROWS when doing CREATE TABLE.
myisam_stats_method = How the server treats NULL values when collecting stats about distribution of index values for MyISAM tables. Values are: nulls_equal all NULL index values are considered equal and form a single value group that has a size equal to the number of NULL values
nulls_unequal NULL values are considered unequal, each NULL forms a distinct value group of size 1.
nulls_ignored, NULL values are ignored.
myisam_use_mmap = added in 5.1.4, use memory mapping for reading/writing MyISAM tables.

18. Repairing MyISAM Tables
myisam_recover_options (FORCE,BACKUP)
myisam_repair_threads (1)
multi-threaded repair by sorting is beta-quality
recover_options=recovery mode. Values = any combination of the values of DEFAULT, BACKUP, FORCE, or QUICK, separated by commas. Specifying with no argument is the same as specifying DEFAULT, and specifying with an explicit value of "" disables recovery (same as not giving the option).
If recovery is enabled, each time mysqld opens a MyISAM table, it checks whether the table is marked as crashed or wasn't closed properly. If this is the case, mysqld runs a check on the table. If the table was corrupted, mysqld attempts repair.
The following options affect how the repair works:
BACKUP If the data file was changed during recovery, save a backup of the tbl_name.MYD file as tbl_name-datetime.BAK.
FORCE Run recovery even if we would lose more than one row from the .MYD file.
QUICK = Don't check the rows in the table if there aren't any delete blocks.
DEFAULT = Recovery w/out backup, forcing, quick checking.
Before the server automatically repairs a table, it writes a note about the repair to the error log. If you want to be able to recover from most problems without user intervention, you should use the options BACKUP,FORCE. This forces a repair of a table even if some rows would be deleted, but it keeps the old data file as a backup so that you can later examine what happened.

19. MyISAM Index Sorting
Done with REPAIR TABLE, ALTER TABLE, LOAD DATA INFILE, CREATE INDEX
myisam_sort_buffer_size (56M)
myisam_max_sort_file_size (10G)
myisam_sort_buffer_size = buffer size for sorting indexes during REPAIR TABLE or adding a new index to an existing table w/data. max is 4Gb before , 16,384 petabytes and later, assuming 64-bit. 64-bit windows limit is 4Gb no matter what version, larger values are truncated.
myisam_max_sort_file_size = max temp file when re-creating a MyISAM index during repair, ALTER TABLE or LOAD DATA INFILE. If bigger than this, index is created using key_cache instead, which takes longer.

20. FULLTEXT search MyISAM only ft_min_word_len (4) ft_max_word_len (84)
ft_stopword_file (built-in)
ft_stopword_file – defined in the source code in the storage/myisam/ft_static.c, or specify a file. Comments (C style) aren't honored, but all words in the file are used. If you set this to '', there is no stopword filtering. ie, “is”, “the”, etc. – common words.

21. FULLTEXT search ft_boolean_syntax (+ -><()~*:""&|)
ft_query_expansion_limit (20)
ft_boolean_syntax = list of operators supported by boolean full-text searches (using IN BOOLEAN MODE). See Section , “Boolean Full-Text Searches”
The default variable value is '+ -><()~*:""&|'. The rules for changing the value are as follows:
Operator function is determined by position within the string.
The replacement value must be 14 characters.
Each character must be an ASCII nonalphanumeric character.
Either the 1st or 2nd character must be a space.
No duplicates are allowed except the phrase quoting operators in positions 11 and 12. These two characters are not required to be the same, but they are the only two that may be.
Positions 10, 13, and 14 (which by default are set to “:”, “&”, and “|”) are reserved for future extensions.
ft_query_expansion_limit = The number of top matches to use for full-text searches performed using WITH QUERY EXPANSION. “It works by performing the search twice, where the search phrase for the 2nd search is the original search phrase concatenated with the few most highly relevant docs from the first search. Thus, if one of these docs contains the word “database” and the word “MySQL”, the second search finds the documents that contain the word “MySQL” even if they do not contain the word “database”.”
see

22. MyISAM Key Cache Can have more than one CACHE INDEX IN .....
key_buffer_size (16M)
key_cache_block_size (1024)
key_buffer_size, key_cache_block_sizecan be set per named cache using SET GLOBAL cachename.variable=value, ie
SET GLOBAL session.key_buffer_size=10240;

23. MyISAM Key Cache Uses LRU; hot/warm sub-chains
key_cache_age_threshold (300)
key_cache_division_limit (100)
key_cache_division_limit and key_cache_age_threshold can be set per named cache using SET GLOBAL cachename.variable=value.
age_threshold = how fast something gets demoted from “hot” to “warm” sub-chain
division_limit – % of key cache to use in warm (vs. hot) sub-chain of the cache

24. MyISAM Key Cache Sizing
Percentage used for all key caches:
1 – (Key_blocks_unused * key_cache_block_size) / key_buffer_size)
1 – (13360 * 1024)/16*1024*1024 = bytes
Key_blocks_used(36)
max used at any time
Key_blocks_not_flushed (0)

25. MyISAM Key Cache Efficiency
Cache miss %
Key_reads (from disk) / Key_read_requests * 100
34 / *100 = 0.01 %
Key_write_requests (10)
Key_writes (10)

26. Transaction Basics autocommit (ON) tx_isolation (READ-COMMITTED)
completion-type (0)
completion-type – Best left alone – default 0 = COMMIT
if 1, COMMIT = COMMIT AND CHAIN (open new txn), same with ROLLBACK.
If 2, COMMIT = COMMIT RELEASE (close session), same with ROLLBACK

27. Transaction Basics foreign_key_checks (ON, session only)
transaction_prealloc_size (4 Kb)
Starting/ending size of a shared per- transaction memory pool
transaction_alloc_block_size (8 Kb)
if a per-transaction memory pool needs more memory, increase by this much

28. InnoDB Basics innodb_data_file_path (ibdata_primary:128M:autoextend)
innodb_autoextend_increment (8)
innodb_data_home_dir ()

29. InnoDB Flags ignore_builtin_innodb (OFF)
innodb_flush_log_at_trx_commit (1)
innodb_fast_shutdown (1)
ignore_builtin_innodb – as opposed to plugin
innodb_flush_log_at_trx_commit
0 = log buffer written once per second and flushed
1 = log buffer written at each commit, flush to disk
2 = log buffer written at each commit, flush to disk once per second
fast_shutdown
0 = full purge, insert buffer merge before shutdown. can take a long time.
1 = skips at shutdown
2 = flushes logs and shuts down cold, as if a crash. No commit txn will be lost, but crash recovery will be done on startup.

30. InnoDB Flags innodb_file_per_table (ON)
innodb_locks_unsafe_for_binlog (OFF)
innodb_stats_on_metadata (ON)
innodb_use_legacy_cardinality_algorithm (ON)
innodb_stats_on_metadata
When on, as default and before , InnoDB updates statistics during metadata statements such as SHOW TABLE STATUS or SHOW INDEX, or when accessing the INFORMATION_SCHEMA tables TABLES or STATISTICS.
When disabled, InnoDB does not updates statistics during these operations. Disabling this variable can improve access speed for schemas that have a large number of tables or indexes.
innodb_use_legacy_cardinality_algorithm (5.1.35)
With OFF, better randomization of index cardinality

31. InnoDB Flags innodb_adaptive_hash_index (ON) innodb_checksums (ON)
innodb_autoinc_lock_mode (1)
checksums are a safety feature. The manual says you may want to turn off for benchmarks.
lock mode of 1 (“consecutive), ensures that, in the presence of INSERT statements where the number of rows is not known in advance (and where auto-increment numbers are assigned as the statement progresses), all auto-increment values assigned by any “INSERT-like” statement are consecutive, and operations are safe for statement-based replication.
lock mode of 2 = interleaved, not good for statement-based replication
lock mode of 0 = way it was before , only use for testing/backwards compatibility.

32. InnoDB Flags innodb_force_recovery (0) innodb_table_locks (ON)
innodb_support_xa (ON)
force recovery – only set if you're actually trying to recover from a crash and the InnoDB table is corrupt. then, a value from 1-6.

33. InnoDB Flags innodb_lock_wait_timeout (240)
innodb_rollback_on_timeout (OFF)
timed_mutexes (OFF)
unique_checks (ON)
Innodb_lock_wait_timeout – how long InnoDB will wait for a row-level lock.
rollback on timeout – if ON, entire txn is rolled back when there's a timeout. Otherwise, only the previous statement is rolled back.
timed_mutexes – whether or not SHOW ENGINE INNODB MUTEX shows time in ms or just shows 0.
unique_checks – session variable only. if set to 0, large table imports in InnoDB can be speeded up, but uniqueness violations may occur. If set to 1 (the default), uniqueness checks for secondary indexes in InnoDB tables are performed. Note that even if set to 0, a storage engine is still allowed to check for them and issue duplicate-key errors if it detects them.

34. InnoDB Doublewrite innodb_doublewrite (ON)
Innodb_dblwr_writes (592,341)
Innodb_dblwr_pages_written (4,537,224)
Doublewrite means that before writing pages to a data file, InnoDB first writes them to a contiguous tablespace area called the doublewrite buffer. Only after the write and the flush to the doublewrite buffer has completed does InnoDB write the pages to their proper positions in the data file. If the operating system crashes in the middle of a page write, InnoDB can later find a good copy of the page from the doublewrite buffer during recovery.

35. InnoDB Concurrency Variables
innodb_thread_concurrency (16)
innodb_commit_concurrency (0)
innodb_concurrency_tickets (500)
innodb_sync_spin_loops (20)
innodb_thread_concurrency – Max value= disables the checking of thread concurrency. After x OS threads are in innodb, any more are put into a waiting queue.
innodb_commit_concurrency – 0 is for “unlimited”
innodb_concurrency_tickets – # times a thread can enter InnoDB without having to be queued if the threads exceed the value of innodb_thread_concurrency
sync_spin_loops – how many times to wait for a mutex to be freed before suspending the thread

36. InnoDB Buffer Pool innodb_buffer_pool_size (8G)
innodb data/index cache
Innodb_page_size (16 Kb)
Innodb_buffer_pool_pages_total (524,288)
Innodb_buffer_pool_pages_data (46,905)
Innodb_buffer_pool_pages_free (477177)
Innodb_buffer_pool_pages_misc (206)
According to this, you are under-utilizing your InnoDB buffer pool.
misc pages are pages used for admin overhead, ie row locks & adaptive hash

37. Dirty Pages innodb_max_dirty_pages_pct (90)
after this % is reached, wait while dirty pages are flushed to disk
Innodb_buffer_pool_wait_free (0)
Innodb_buffer_pool_pages_dirty (9)
Included in the Innodb_buffer_pool_pages_data
wait free is a counter for the # of times the buffer pool had to wait for pages to be freed by cleanup

38. Flush / Sync Innodb_buffer_pool_pages_flushed (4,537,224)
counter of # times flushed
Innodb_data_fsyncs (10,201,211)
Innodb_data_pending_fsyncs (0)
if buffer_pool_pages_flushed is a lot, there's a lot of disk I/O. Writes may not be done in batches that correspond to pages.

39. InnoDB Row Locks Innodb_row_lock_waits (269)
Innodb_row_lock_current_waits (0)
Innodb_row_lock_time (31,637 ms)
Innodb_row_lock_time_avg (117 ms)
Innodb_row_lock_time_max (4,599 ms)

40. InnoDB Reads Innodb_buffer_pool_read_requests (1,360,965,036)
Innodb_buffer_pool_reads (27,482)
reads buffer pool could not do & single page read
Innodb_data_reads (28,754)
Innodb_data_pending_reads (0)

41. InnoDB Reads Innodb_data_read (695.47 Mb) Innodb_pages_read (44,377)
Innodb_rows_read (2,721,225,514)

42. InnoDB Writes Innodb_buffer_pool_write_requests (47,307,349)
Innodb_data_writes (12,468,811)
Innodb_data_pending_writes (0)

43. InnoDB Writes Innodb_data_written (153 Gb)
Innodb_pages_written (4,537,224)
Innodb_pages_created (3,664)

44. InnoDB Rows Written Innodb_rows_inserted (32,681)
Innodb_rows_deleted (1,555,539)
Innodb_rows_updated (3,908,062)

45. InnoDB Log Basics innodb_log_file_size (1G)
innodb_log_files_in_group (3)
innodb_mirrored_log_groups (1)
innodb_log_group_home_dir (./)

46. InnoDB Logs innodb_log_buffer_size (8M) Innodb_log_waits (0)
Innodb_os_log_fsyncs (8,464,144)
Innodb_os_log_pending_fsyncs (0)
innodb_log_buffer_size – “sensible values range from 1Mb – 8Mb” according to the manual. “A large log buffer allows large transactions to run without a need to write the log to disk before the transactions commit. Thus, if you have big transactions, making the log buffer larger saves disk I/O.”
If log_buffer_size too small, there will be Innodb_log_waits

47. InnoDB Log Writes Innodb_log_write_requests (26,175,407)
Innodb_os_log_pending_writes (0)
Innodb_os_log_written (14.42 Gb)

48. Other InnoDB Variables
innodb_additional_mem_pool_size (16Mb)
innodb_open_files (300)
innodb_thread_sleep_delay (10,000 = .01 sec)
additional_mem_pool_size – additional memory for things like the data dictionary. If this value is too small, warnings will be written to the error log and more memory will be allocated from the OS. Default is 1 Mb.
innodb_open_files – file descriptors for .ibd files. do not affect table_open_cache, variable is independent of other open files limits.
innodb_thread_sleep_delay – how long (microseconds) a thread waits before joining the InnoDB queue

49. Advanced InnoDB Variables
innodb_flush_method ()
innodb_max_purge_lag (0)
fsync() by default to flush data files & logs
O_DSYNC = O_SYNC to open and flush logs, fsync() for data files.
O_DIRECT (some GNU/Linux versions, FreeBSD, and Solaris), O_DIRECT (or directio() on Solaris) to open the data files, fsync() to flush data files and logs.
This variable is relevant only for Unix. On Windows, the flush method is always async_unbuffered and cannot be changed.
purge lag = if # of txns that UPDATE or DELETE is > this, then delay a while before proceeding. 0 means no delay ever.

50. InnoDB Status for Performance
Innodb_buffer_pool_read_ahead_rnd (16)
Innodb_buffer_pool_read_ahead_seq (286)
Innodb_buffer_pool_read_ahead_rnd:
Number of random read-aheads, for when a large part of the table is scanned, in random order
Innodb_buffer_pool_read_ahead_seq: Number of sequential read-aheads, for sequential full table scan
High rates of these are both bad.

51. Percona patch extensions
XtraDB
Percona build of MySQL
(5.x.xx-percona-log)
Standard and InnoDB Plugin
Slides are current up to percona-log
xtradb:reference:variables:alphabetically
Up to percona-log
All are global and can be set in my.cnf
Many are dynamic, see the wiki for more info
Percona did a great job of keeping the variable defaults so they'd work the same as InnoDB does. We've found improvements in performance even when none of these variables are tweaked!

52. I/O Extensions innodb_read_io_threads innodb_write_io_threads
innodb_io_capacity
innodb_use_purge_thread
read_io_threads: The number of background I/O threads for read prefetch requests. Default 1, range 1-64.
write_i/o threads. The number of background I/O threads for writing dirty pages from the buffer pool. Default 1, range 1-64.
you can see them in the FILE I/O part of SHOW ENGINE INNODB STATUS on xtradb
io_capacity - # of disk I/O operations InnoDB assumes the server can perform per second. The patch adjusts InnoDB's behavior to consume more I/O resources when it's told they are available.
Default 100 – how innodb works
Allowed values 100 ~ 999,999,999
use_purge_thread, default is 0 through InnoDB plugin and 1 starting Range is 0-64

53. More I/O extensions innodb_ibuf_accel_rate innodb_ibuf_active_contract
innodb_ibuf_max_size
Ibuf = insert buffer
innodb_ibuf_accel_rate – if innodb_io_capacity isn't enough to tune the insert buffer, you can also fine-tune it using this. Default 100, 0-999,999,999
innodb_ibuf_active_contract - Default 0(~1.0.5), 1(1.0.6~). 0 means do not contract the size of the insert buffer until you reach max size. 1 makes each user thread contract the insert buffer as possible in asynchronous.
innodb_ibuf_max_size – default is ½ size of innodb buffer pool. Range is less than that, starting with = very small, and very small values aren't good for performance. If you use very fast storage, small value (like several MB) may show better performance.“very fast storage” means much faster than HDD based storage (any RAID storages). It is like the battery-backed huge dynamic memory array etc… So, it is not recommended to set the value for performance, if the storage doesn't have ram-level speed/response, the performance will drop down.

54. More I/O extensions innodb_enable_unsafe_group_commit
innodb_flush_neighbor_pages
innodb_read_ahead
none
random
linear
both
innodb_enable_unsafe_group_commit – bug fixed in XtraDB 1.0.6, so not needed. Default is 0,
1 forces group commit even if with binlog. If 1 is set, InnoDB-transaction log order and binlog order may not be same. In this case, if you use some hot-backup of InnoDB, the snapshot may not correspond to any binlog position. WHAT BUG WAS FIXED BY THIS?
Flush neighbor pages – If a dirty page is flushed, should you also flush neighbor pages in the same data file? Default 1, but 0 is better for disks that don't have delays due to head seeking, like SSD's, or if you have lots of write-buffering.
innodb_read_ahead
Control native read-ahead behavior of InnoDB. 'none':disable read-ahead, 'random':enable read-ahead for random access only, 'linear':enable read-ahead for sequential access only, 'both':enable both of read-ahead feature.
Default 'both'
“read-ahead for random access” is removed from Plugin So also XtraDB ignores it after
I think the idea is better performance, you probably usually set this to linear 'cause that makes sense.

55. Checkpointing innodb_adaptive_checkpoint innodb_checkpoint_age_target
Adaptive checkpointing changes when blocks are flushed to disk. Instead of flushing when reaching max_dirty_pages_pct, flushed based on the age of the block. Default value is none, how InnoDB works. Reflex, If there is a block that is ½ the max age, start “weak” flushing of all blocks. If a block is ¾ max age, start “strong” flushing. Strength is based on io_capacity, so if you use reflex you need to tune that.
'estimate': If the oldest block age > 1/2 of the max age capacity, flush a # of blocks every second. The number of the blocks is determined by [number of modified blocks], [LSN progress speed] and [average age of all modified blocks]. independent from innodb_io_capacity. experimental
innodb_checkpoint_age_target – 0 (default): disable the feature. max_checkpoint_age_async can be controlled by this value. It is not needed to shrink innodb_log_file_size to tune recovery time. ????
and the LOG section of SHOW ENGINE INNODB STATUS - “max checkpoint age“, “modified age” and “checkpoint age“

56. SHOW ENGINE INNODB STATUS
BUFFER POOL AND MEMORY
Total memory allocated ; in additional pool allocated
+ Internal hash tables (constant factor + variable factor)
+ Adaptive hash index ( )
+ Page hash
+ Dictionary cache ( )
+ File system ( )
+ Lock system ( )
+ Recovery system (0 + 0)
+ Threads ( )
Buffer pool size
+ Buffer pool size, bytes
Free buffers
Database pages
Modified db pages
Pending reads 0
Added extended information of InnoDB internal hash tables sizes (in bytes) in BUFFER POOL AND MEMORY section. It also adds Buffer pool size in bytes information.

57. Statistics/Info innodb_show_locks_held innodb_show_verbose_locks
innodb_stats_auto_update
innodb_stats_method
innodb_stats_update_need_locks
innodb_show_verbose_locks - Whether to show records locked in SHOW INNODB STATUS
innodb_show_locks_held - Number of locks held to print for each InnoDB transaction in SHOW INNODB STATUS. (see bugs.mysql.com/bug.php?id=29126s
innodb_stats_method – similar to myisam_stats_method (see slide 17) ('nulls_equal', 'nulls_unequal', 'nulls_ignored'). But InnoDB doesn't have several patterns of statistics currently. So, though this option able to be changed dynamically, we need re-calculate statistics to change the method for the table. (HUH?)
innodb_stats_update_need_locks - (default 1) - If you meet contention of &dict_operation_lock, setting 0 reduces the contention. But 0 disables to update “Data_free:” of “show table status”.
innodb_stats_auto_update - (default 1) - InnoDB updates the each index statistics automatically. Setting this option 0 can stop these automatic recalculation of the statistics except for “first open” and “ANALYZE TABLE command”.

58. New in INFORMATION_SCHEMA
innodb_table_stats
innodb_index_stats
GET EXAMPLES!!!
table_name table name in InnoDB internal style ('database/table')
rows estimated number of all rows
clust_size cluster index (table/primary key) size in number of pages
other_size other index (non primary key) size in number of pages
modified internal counter to judge whether statistics recalculation should be done
If the value of modified column exceeds “rows / 16” or , the statistics recalculation is done when innodb_stats_auto_update == 1. We can estimate the oldness of the statistics by this value.
innodb_index_stats - shows index statistics information of dictionary cached.
Field Notes
index_name index name
fields How many fields the index key has. (it is internal structure of InnoDB, it may be larger than the 'CREATE TABLE')
row_per_keys estimate rows per 1 key value. ([1 column value], [2 columns value], [3 columns value], …)
index_size index size in pages
leaf_pages number of leaf pages

59. Recovery innodb_fast_recovery innodb_recovery_stats
innodb_fast_recovery - buf_flush_insert_sorted_into_flush_list() hack not to sorting (new variable innodb_fast_recovery (default false(~1.0.5), true(1.0.6~)) - if set true, the hack is enabled.)
MORE WORK NEEDED
More recovery stats (default, I think.)

60. Recovery Stats
RECOVERY STATISTICS
Recovery time: 18 sec. (1 turns)
Data page IO statistics
Requested pages: 9126
Read pages:
Written pages:
(Dirty blocks): 1156
Grouping IO [times]:
number of pages,
read request neighbors (in 32 pages chunk),
combined read IO,
combined write IO
1, 32, ,
2, 0, , 97
3, 7, ,
4, 4, ,
....
64, 0, ,
innodb_fast_recovery - buf_flush_insert_sorted_into_flush_list() hack not to sorting (new variable innodb_fast_recovery (default false(~1.0.5), true(1.0.6~)) - if set true, the hack is enabled.)

61. Recovery Stats
Recovery process statistics
Checked pages by doublewrite buffer: 128
Overwritten pages from doublewrite: 0
Recovered pages by io_thread:
Recovered pages by main thread:
Parsed log records to apply:
Sum of the length:
Applied log records:
Sum of the length:
Pages which are already new enough: 93
Oldest page's LSN:
Newest page's LSN:
innodb_fast_recovery - buf_flush_insert_sorted_into_flush_list() hack not to sorting (new variable innodb_fast_recovery (default false(~1.0.5), true(1.0.6~)) - if set true, the hack is enabled.)

62. Other Extensions innodb_thread_concurrency_timer_based
innodb_relax_table_creation
innodb_extra_rsegments
INFORMATION_SCHEMA.innodb_rseg
Relax table creation – default 0, values are 0 or 1. Dynamic, global.
extra_rsegments - (default 0) - The number of extra user rollback segments created when new db is created.
Information schema added – innodb_rseg
GET EXAMPLE
shows information about all rollback segments
Field Notes
rseg_id rollback segment id
space_id space where the segment placed
zip_size compressed page size in bytes if compressed otherwise 0
page_no page number of the segment header
max_size max size in pages
curr_size current size in pages

63. Other Extensions innodb_dict_size_limit Innodb_dict_tables
innodb_expand_import
innodb_extra_undoslots
innodb_overwrite_relay_log_info
dict_size_limit: for memory. default is 0, unlimited. Data dictionary can grow large. Innodb_dict_tables is status variable with # entries in the cache.
expand_import: convert .ibd using .exp info when doing IMPORT TABLESPACE, when this is 1. default is 0. Use this to change indexes quickly.
extra_undo_slots – Only for err “Warning: cannot find a free slot for an undo log”. If true, up to 4072 undo slots. If false, MySQL default is 1024 undo slots, default is false.
overwrite_relay_log_info: The position of replication is updated after InnoDB commit of the transaction on the slave. If a crash occurs after the commit but before the replication position update, the committed transaction is executed again after the crash recovery. If this is set to true, the relay log file will be overwritten with the value (later position). Default is false, because you might end up skipping statements from other storage engines.

64. Win a signed copy of Sheeri’s book.
Thank You.
Win a signed copy of Sheeri’s book.
Leave your business card and you could win a book. We’ll invite you to read our blog posts, follow us on twitter, and join our next webinars.
Drawing will be immediately after the talk once all cards are collected.
- Successful growing business for more than 10 years
- Served many customers with complex requirements/infrastructure just like yours.
- Operate globally for 24 x 7 “always awake” services 64

65. Thank You Sheeri Cabral Questions, Comments, Feedback?
Blog:
Ask me about saving 15% on our Adoption Accelerator for MySQL
while at MySQL Conference 2010! 65