When the variable innodb_recovery_stats is enabled and XtraDB has to do recovery on startup, server will write detailed recovery statistics information to the error log. This info will be written after the recovery process is finished.
Example of output statistics for recovery process:
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RECOVERY STATISTICS
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Recovery time: 18 sec. (1 turns)
Data page IO statistics
Requested pages: 9126
Read pages: 9126
Written pages: 7957
(Dirty blocks): 1156
Grouping IO [times]:
number of pages,
read request neighbors (in 32 pages chunk),
combined read IO,
combined write IO
1, 32, 335, 548
2, 0, 121, 97
3, 7, 49, 44
4, 4, 43, 26
....
64, 0, 2, 25
Recovery process statistics
Checked pages by doublewrite buffer: 128
Overwritten pages from doublewrite: 0
Recovered pages by io_thread: 9145
Recovered pages by main thread: 0
Parsed log records to apply: 2572491
Sum of the length: 71274689
Applied log records: 2376356
Sum of the length: 68098300
Pages which are already new enough: 93
Oldest page's LSN: 926917970
Newest page's LSN: 1526578232
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