If, in Percona Server, you are observing tail latencies on queries that should be fast, this might be a side effect of Percona's improved InnoDB Empty Free List Algorithm.  When using this algorithm (the default in 5.6 and 5.7 and optional configuration in 8.0), a query needing a free page while none are available waits until the LRU Manager Thread refills the free list.  Because this

Yves Trudeau and Francisco Bordenave, MySQL experts at Percona, recently published a three-part post: (1) Give Love to Your SSDs – Reduce innodb_io_capacity_max!; (2) InnoDB Flushing in Action for Percona Server for MySQL; (3) Tuning MySQL/InnoDB Flushing for a Write-Intensive Workload. It’s a fantastic read from start to finish, and it made me realize: dirty pages sound bad, but they are good. I suspect the opposite (“dirty pages are not good”) is a misconception due to an incomplete picture. Let’s complete the picture.

Yves Trudeau and Francisco Bordenave, MySQL experts at Percona, recently published a three-part post: (1) Give Love to Your SSDs – Reduce innodb_io_capacity_max!; (2) InnoDB Flushing in Action for Percona Server for MySQL; (3) Tuning MySQL/InnoDB Flushing for a Write-Intensive Workload. It’s a fantastic read from start to finish, and it made me realize: dirty pages sound bad, but they are good. I suspect the opposite (“dirty pages are not good”) is a misconception due to an incomplete picture. Let’s complete the picture.

The Log Buffer Edition once again is sparkling with some gems, hand-picked from Oracle, SQL Server and MySQL.

Oracle:

• Oracle GoldenGate 12.1.2.1.1  is now certified with Unity 14.10.  With this certification, customers can use Oracle GoldenGate to deliver data to Teradata Unity which can then automate the distribution of data to multiple Teradata databases.
• How do I change DNS servers on Exadata storage servers.
• Flushing Shared Pool Does Not Slow Its Growth.
• …

In MySQL 5.6.2 we have introduced a new background thread named the page_cleaner in InnoDB. Adaptive flushing of modified buffer pool pages in the main background thread, async flushing by a foreground query thread if the log files are near to wrapping around, idle flushing and shutdown flushing are now moved to this thread, leaving only the last resort sync flushing in foreground query threads. We’ve also added counters for these activities.

As page_cleaner is all about the flushing of dirty pages to disk it’ll do you a world of good if you can go through this post where I have explained different types of flushing that happen inside InnoDB and the conditions that trigger flushing. The page_cleaner thread is only concerned with flush_list flushing (this may change in future releases). So let us dig a bit deeper into why …