Extended show engine InnoDB status¶
This feature reorganizes the output of SHOW ENGINE INNODB STATUS
to improve readability and to provide additional information. The
variable innodb_show_locks_held controls the umber of
locks held to print for each InnoDB transaction.
This feature modified the SHOW ENGINE INNODB STATUS command as follows:
-
Added extended information about InnoDB internal hash table sizes (in bytes) in the
BUFFER POOL AND MEMORYsection; also added buffer pool size in bytes. -
Added additional LOG section information.
Other information¶
- Author / Origin: Baron Schwartz, https://lists.mysql.com/internals/35174
System variables¶
innodb_show_locks_held¶
| Option | Description |
|---|---|
| Command-line | Yes |
| Config file | Yes |
| Scope | Global |
| Dynamic | Yes |
| Data type | ULONG |
| Default | 10 |
| Range | 0 - 1000 |
Specifies the number of locks held to print for each InnoDB transaction in
SHOW ENGINE INNODB STATUS.
innodb_print_lock_wait_timeout_info¶
| Option | Description |
|---|---|
| Command-line | Yes |
| Config file | Yes |
| Scope | Global |
| Dynamic | Yes |
| Data type | Boolean |
| Default | OFF |
Makes InnoDB to write information about all lock wait timeout errors into the log file.
This allows to find out details about the failed transaction, and, most
importantly, the blocking transaction. Query string can be obtained from EVENTS_STATEMENTS_CURRENT table, based on the
PROCESSLIST_ID field, which corresponds to thread_id from the log
output.
Taking into account that blocking transaction is often a multiple statement one, following query can be used to obtain blocking thread statements history:
SELECT s.SQL_TEXT FROM performance_schema.events_statements_history s
INNER JOIN performance_schema.threads t ON t.THREAD_ID = s.THREAD_ID
WHERE t.PROCESSLIST_ID = %d
UNION
SELECT s.SQL_TEXT FROM performance_schema.events_statements_current s
INNER JOIN performance_schema.threads t ON t.THREAD_ID = s.THREAD_ID
WHERE t.PROCESSLIST_ID = %d;
The PROCESSLIST_ID in this example is exactly the thread id from error log output.
Status variables¶
The status variables here contain information available in the output of SHOW
ENGINE INNODB STATUS, organized by the sections SHOW ENGINE INNODB STATUS
displays. If you are familiar with the output of SHOW ENGINE INNODB STATUS,
you will probably already recognize the information these variables contain.
BACKGROUND THREAD¶
The following variables contain information in the BACKGROUND THREAD
section of the output from SHOW ENGINE INNODB STATUS.
Expected output
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 1 srv_active, 0 srv_shutdown, 11844 srv_idle
srv_master_thread log flush and writes: 11844
InnoDB has a source thread which performs background tasks depending on the server state, once per second. If the server is under workload, the source thread runs the following: performs background table drops; performs change buffer merge, adaptively; flushes the redo log to disk; evicts tables from the dictionary cache if needed to satisfy its size limit; makes a checkpoint. If the server is idle: performs background table drops, flushes and/or checkpoints the redo log if needed due to the checkpoint age; performs change buffer merge at full I/O capacity; evicts tables from the dictionary cache if needed; and makes a checkpoint.
Innodb_master_thread_active_loops¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the number of times the above one-second loop was executed for active server states.
Innodb_master_thread_idle_loops¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the number of times the above one-second loop was executed for idle server states.
Innodb_background_log_sync¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the number of times the InnoDB source thread has written and flushed the redo log.
SEMAPHORES¶
The following variables contain information in the SEMAPHORES section of
the output from SHOW ENGINE INNODB STATUS. An example of that output is:
Expected output
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 9664, signal count 11182
Mutex spin waits 20599, rounds 223821, OS waits 4479
RW-shared spins 5155, OS waits 1678; RW-excl spins 5632, OS waits 2592
Spin rounds per wait: 10.87 mutex, 15.01 RW-shared, 27.19 RW-excl
INSERT BUFFER AND ADAPTIVE HASH INDEX¶
The following variables contain information in the INSERT BUFFER AND ADAPTIVE
HASH INDEX section of the output from SHOW ENGINE INNODB STATUS. An
example of that output is:
Expected output
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 6089, seg size 6091,
44497 inserts, 44497 merged recs, 8734 merges
0.00 hash searches/s, 0.00 non-hash searches/s
Innodb_ibuf_free_list¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
Innodb_ibuf_segment_size¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
LOG¶
The following variables contain information in the LOG section of the
output from SHOW ENGINE INNODB STATUS. An example of that output is:
Expected output
LOG
---
Log sequence number 10145937666
Log flushed up to 10145937666
Pages flushed up to 10145937666
Last checkpoint at 10145937666
Max checkpoint age 80826164
Checkpoint age target 78300347
Modified age 0
Checkpoint age 0
0 pending log writes, 0 pending chkp writes
9 log i/o's done, 0.00 log i/o's/second
Log tracking enabled
Log tracked up to 10145937666
Max tracked LSN age 80826164
Innodb_lsn_current¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the current log sequence number.
Innodb_lsn_flushed¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the current maximum LSN that has been written and flushed to disk.
Innodb_lsn_last_checkpoint¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the LSN of the latest completed checkpoint.
Innodb_checkpoint_age¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the current InnoDB checkpoint age, i.e., the difference between the current LSN and the LSN of the last completed checkpoint.
Innodb_checkpoint_max_age¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the maximum allowed checkpoint age above which the redo log is close to full and a checkpoint must happen before any further redo log writes.
Note
This variable was removed in Percona Server for MySQL 8.0.13-4 due to a change in MySQL. The variable is identical to log capacity.
BUFFER POOL AND MEMORY¶
The following variables contain information in the BUFFER POOL AND MEMORY
section of the output from SHOW ENGINE INNODB STATUS. An example of that
output is:
Expected output
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 137363456; in additional pool allocated 0
Total memory allocated by read views 88
Internal hash tables (constant factor + variable factor)
Adaptive hash index 2266736 (2213368 + 53368)
Page hash 139112 (buffer pool 0 only)
Dictionary cache 729463 (554768 + 174695)
File system 824800 (812272 + 12528)
Lock system 333248 (332872 + 376)
Recovery system 0 (0 + 0)
Dictionary memory allocated 174695
Buffer pool size 8191
Buffer pool size, bytes 134201344
Free buffers 7481
Database pages 707
Old database pages 280
Modified db pages 0
Pending reads 0
Pending writes: LRU 0, flush list 0 single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 707, created 0, written 1
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 707, unzip_LRU len: 0
Innodb_mem_adaptive_hash¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the current size, in bytes, of the adaptive hash index.
Innodb_mem_dictionary¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the current size, in bytes, of the InnoDB in-memory data dictionary info.
Innodb_mem_total¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the total amount of memory, in bytes, InnoDB has allocated in the process heap memory.
Innodb_buffer_pool_pages_LRU_flushed¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the total number of buffer pool pages which have been flushed from the LRU list, i.e., too old pages which had to be flushed in order to make buffer pool room to read in new data pages.
Innodb_buffer_pool_pages_made_not_young¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the number of times a buffer pool page was not marked as accessed recently in the LRU list because of innodb_old_blocks_time variable setting.
Innodb_buffer_pool_pages_made_young¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the number of times a buffer pool page was moved to the young end of the LRU list due to its access, to prevent its eviction from the buffer pool.
Innodb_buffer_pool_pages_old¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the total number of buffer pool pages which are considered to be old according to the Making the Buffer Pool Scan Resistant manual page.
TRANSACTIONS¶
The following variables contain information in the TRANSACTIONS section of
the output from SHOW INNODB STATUS. An example of that output is:
Expected output
------------
TRANSACTIONS
------------
Trx id counter F561FD
Purge done for trx's n:o < F561EB undo n:o < 0
History list length 19
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started, process no 993, OS thread id 140213152634640
mysql thread id 15933, query id 32109 localhost root
show innodb status
---TRANSACTION F561FC, ACTIVE 29 sec, process no 993, OS thread id 140213152769808 updating or deleting
mysql tables in use 1, locked 1
Innodb_max_trx_id¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the next free transaction id number.
Innodb_oldest_view_low_limit_trx_id¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the highest transaction id, above which the current oldest open read view does not see any transaction changes. Zero if there is no open view.
Innodb_purge_trx_id¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
This variable shows the oldest transaction id whose records have not been purged yet.
Innodb_purge_undo_no¶
| Option | Description |
|---|---|
| Scope | Global |
| Data type | Numeric |
INFORMATION_SCHEMA Tables¶
The following table contains information about the oldest active transaction in the system.
INFORMATION_SCHEMA.XTRADB_READ_VIEW¶
| Column Name | Description |
|---|---|
| ‘READ_VIEW_LOW_LIMIT_TRX_NUMBER’ | This is the highest transactions number at the time the view was created. |
| ‘READ_VIEW_UPPER_LIMIT_TRX_ID’ | This is the highest transactions ID at the time the view was created. This means that it should not see newer transactions with IDs bigger than or equal to that value. |
| ‘READ_VIEW_LOW_LIMIT_TRX_ID’ | This is the latest committed transaction ID at the time the oldest view was created. This means that it should see all transactions with IDs smaller than or equal to that value. |
Note
Starting with Percona Server for MySQL 8.0.20-11, in INFORMATION_SCHEMA.XTRADB_READ_VIEW, the data type for the following columns is changed from VARCHAR(18) to BIGINT UNSIGNED:
-
READ_VIEW_LOW_LIMIT_TRX_NUMBER -
READ_VIEW_UPPER_LIMIT_TRX_ID -
READ_VIWE_LOW_LIMIT_TRX_ID
The columns contain 64-bit integers, which is too large for VARCHAR(18).
The following table contains information about the memory usage for InnoDB/XtraDB hash tables.
INFORMATION_SCHEMA.XTRADB_INTERNAL_HASH_TABLES¶
| Column Name | Description |
|---|---|
| ‘INTERNAL_HASH_TABLE_NAME’ | Hash table name |
| ‘TOTAL_MEMORY’ | Total amount of memory |
| ‘CONSTANT_MEMORY’ | Constant memory |
| ‘VARIABLE_MEMORY’ | Variable memory |
Other reading¶
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