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  1. Percona Server
  2. PS-1753

LP #1631309: performance regression from fix for lp:1433432

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      **Reported in Launchpad by Axel Schwenke last update 30-03-2017 03:03:59

      The fix for lp:1433432 in Percona Server 5.6 introduces a severe performance regression. Sysbench OLTP read-only throughput drops by 50% (single thread) up to 95% (40 threads on a 16-core machine).

      In order to see that, the active set of the database must be slightly bigger than the buffer pool and the workload must access rows in a rather random fashion.

      Here are some numbers. Command line:
      sysbench-0.4.12 --test=oltp --oltp-read-only --oltp-range-size=1000 --oltp-dist-type=uniform --oltp-table-size=1000000 --mysql-socket=/tmp/mysqld.sock.sysbench --mysql-user=root --num-threads=40 --max-time=30 run

      5.6.27: 660 tps
      5.6.28: 36 tps

      This doesn't change when using multiple tables. Performance comes back to normal when the buffer pool is increased. I think this performance regression is too big and too likely to being hit by a real-world user to be ignored. It is quite common that the active set of a database does not fit into the buffer pool.

      Suggestion: roll back commit 6532572a783ea5a025561eda9b1a9350c73405a6

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                lpjirasync lpjirasync (Inactive)
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