XtraDB 5.6 and 5.7: Key Performance Algorithms
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We will discuss selected areas of InnoDB and XtraDB 5.6/5.7 internals: flushing, the relation of buffer pool instance sharding to the XtraDB buffer pool mutex split, priority lock and priority scheduling framework, transaction list management, and performance-related changes in 5.7. We will discuss the motivation behind the changes we did in XtraDB 5.6, their relation to changes done in Oracle InnoDB 5.7, and our plans for XtraDB 5.7. The talk will be technical and assuming familiarity with InnoDB internals. The target audience for the talk would be InnoDB and performance engineers.
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XtraDB 5.6 and 5.7: Key Performance Algorithms
- 1. Laurynas Biveinis Alexey Stroganov Percona Live 2015 XtraDB 5.6 & 5.7: Key Performance Algorithms
- 2. www.percona.com‹#› Agenda InnoDB and XtraDB 5.5, 5.6, 5.7 Algorithms Performance
- 3. www.percona.com‹#› InnoDB 5.5: Buffer Pool Data Structures
- 4. www.percona.com‹#› InnoDB 5.5 solution for the mutex contention
- 5. www.percona.com‹#› XtraDB 5.5 solution for the mutex contention
- 6. www.percona.com‹#› It’s OK to combine the solutions
- 7. www.percona.com‹#› InnoDB 5.5: trx sys trx list
- 8. www.percona.com‹#› XtraDB 5.5: trx sys trx list http://bugs.mysql.com/bug.php?id=49169, https://dev.mysql.com/worklog/task/?id=6578 h"p://bit.ly/pstrx1, h"p://bit.ly/pstrxdesc2
- 9. www.percona.com‹#› Early XtraDB 5.6 vs XtraDB 5.5
- 10. www.percona.com‹#› Early 5.6: now what. Buffer pool mutex contention We have a patch, so we will be fine Right?
- 13. www.percona.com‹#› InnoDB 5.6: page cleaner thread Flushing concentrated there But does it run?
- 14. www.percona.com‹#› XtraDB 5.6: page cleaner thread Prioritize it in the OS scheduler Implemented in Oracle 5.7 too
- 15. www.percona.com‹#› InnoDB 5.6: query thread flushing LRU: single page flush Flush list: sync preflush Query thread flushing: cleaner in trouble So let’s hurt it even more
- 16. www.percona.com‹#› XtraDB 5.6: query thread flushing Disabled —innodb-empty-free-list- algorithm=backoff —innodb-foreground- preflush=exponential_backoff Preflush wait now in Oracle 5.7
- 18. www.percona.com‹#› InnoDB 5.6: cleaner under load Flushing taking > 1s, i.e. 60s… And the other way around Breaks adaptive flushing calculations Long LRU flush prevents flush list flushing
- 19. www.percona.com‹#› XtraDB 5.6: cleaner timeouts Flushing iteration cannot exceed 1s And the other flusher would run, if not for … AF calculations OK http://bugs.mysql.com/bug.php?id=70453
- 20. www.percona.com‹#› InnoDB 5.6: serialized flushing modes Busy cleaner thread:
- 21. www.percona.com‹#› XtraDB 5.6: two-threaded flushing Greatly simplifies heuristics as well
- 22. www.percona.com‹#› InnoDB 5.7: serialised multi-threaded flushing Cleaner Worker Worker Worker Request Flush LRU Flush LRU Flush LRU Flush flush list Flush flush list Flush flush list wait… wait… wait…
- 23. www.percona.com‹#› Serialized Multi-threaded flushing Multi-threaded, and One more thing… LRU and flush list flushing independent No branch has implemented this ATM
- 24. www.percona.com‹#› Buffer pool instance access non- uniformity Mikael Ronstrom: “First the accesses to the buffer pools is in no way evenly spread out” Flushing requests divided uniformly between the instances Acknowledged at 5.5, confirmed in 5.6 5.7 addresses this, but only partially
- 25. www.percona.com‹#› Buffer pool instance access non- uniformity
- 26. www.percona.com‹#› XtraDB 5.6: Buffer pool instance access non-uniformity Instances with empty free lists get extra flushing This is incomplete solution, but helps
- 27. www.percona.com‹#› InnoDB 5.7: Buffer pool instance access non-uniformity Flush list flush request distributed across instances So that target LSN is reached everywhere Is this enough (for the flush list)? What about LRU?
- 28. www.percona.com‹#› InnoDB 5.6: “free buffers 0” Query thread needs a page * - single page flush or sleep Lock buffer pool or free list mutex No free page, unlock, wait (*), goto 1
- 29. www.percona.com‹#› InnoDB 5.6: “free buffers 0” Query thread 1 needs a page Cleaner has a page, does not have the mutex Query thread 2 needs a page Query thread 3 needs a page
- 30. www.percona.com‹#› XtraDB 5.6: “free buffers 0” Priority mutex framework Regardless of the waiting query thread number Cleaner thread gets the mutex first Is able to put a page on the free list
- 31. www.percona.com‹#› 5.7 review XtraDB InnoDB + crc32 for redo log 5.6 late 5.6 + Read view creation 5.5 5.7 + Cleaner thread prioritization 5.6 5.7 + Sync preflush removal 5.6 5.7 (…) + Multi-threaded flushing 5.6 (two-threaded) 5.7 (…) + Non-uniform buffer pool instance flushing 5.6 (…) 5.7 (…) + Buffer pool mutex split 5.1+ + Cleaner thread timeouts 5.6 + Empty free list handling 5.6 + Single page LRU-flush removal 5.6