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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

      Below 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:
              marko Marko Mäkelä
              Reporter:
              baotiao zongzhi chen
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                Updated:

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