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  1. MariaDB Server
  2. MDEV-21423

lock-free trx_sys get performance regression cause by lf_find and ut_delay

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      Hello, guys

      we have port the lock-free trx-sys, however I find that the oltp_read_write case get too much performance regression compare with non-lock-free version..
      Especially when the isolation-level is "read-committed", lock-free trx-sys get about 40% performance regression.
      I guess Mariadb has the same problem..

      This is my sysbench test configure
      bench_type=oltp_read_write;
      threads=560
      tables=8
      table_size=500000

      there is another issue that relate to the lock-free trx_sys
      https://jira.mariadb.org/browse/MDEV-20630?filter=-2

      blow is the sysbench result:
      you can find that the lockfree trx-sys vs non-lockfree trx-sys is
      tps 13405.28 vs 20095.02
      qps 268105.66 vs 401900.40

      lockfree trx-sys : isolation-level

      read-committed

      SQL statistics:
      queries performed:
      read: 33803098
      write: 9658028
      other: 4829014
      total: 48290140
      transactions: 2414507 (13405.28 per sec.)
      queries: 48290140 (268105.66 per sec.)
      ignored errors: 0 (0.00 per sec.)
      reconnects: 0 (0.00 per sec.)

      General statistics:
      total time: 180.1141s
      total number of events: 2414507

      Latency (ms):
      min: 2.96
      avg: 41.75
      max: 4487.73
      95th percentile: 92.42
      sum: 100805088.64

      Threads fairness:
      events (avg/stddev): 4311.6196/167.34
      execution time (avg/stddev): 180.0091/0.01

      non-lockfree: read-committed

      SQL statistics:
      queries performed:
      read: 50672678
      write: 14477908
      other: 7238954
      total: 72389540
      transactions: 3619477 (20095.02 per sec.)
      queries: 72389540 (401900.40 per sec.)
      ignored errors: 0 (0.00 per sec.)
      reconnects: 0 (0.00 per sec.)

      General statistics:
      total time: 180.1161s
      total number of events: 3619477

      Latency (ms):
      min: 2.47
      avg: 27.85
      max: 198.43
      95th percentile: 52.89
      sum: 100798260.68

      Threads fairness:
      events (avg/stddev): 6463.3518/107.19
      execution time (avg/stddev): 179.9969/0.01

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            Assignee:
            svoj Sergey Vojtovich
            Reporter:
            baotiao zongzhi chen
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              Created:
              Updated: