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 thread is
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