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  1. MariaDB Server
  2. MDEV-23407

--temp-pool: change default to 0 and deprecate

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    • Type: Task
    • Status: Closed (View Workflow)
    • Priority: Major
    • Resolution: Duplicate
    • Fix Version/s: N/A
    • Component/s: OTHER
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      Description

      According to benchmarks made by Axel (and further analysis) , this code behind --temp-pool=1 in create_tmp_table() causes a heavy mutex contention:

        if (use_temp_pool && !(test_flags & TEST_KEEP_TMP_TABLES))
          temp_pool_slot = bitmap_lock_set_next(&temp_pool);
      

      The --temp-pool option was implemented to address some bottleneck in Linux kernel, which is reported to be fixed nowadays.

      In MySQL, --temp-pool was deprecated in 5.7 and removed in 8.0.

      Let's do the following:

      • Set --temp-pool=0 by default in MariaDB-10.5 (currently its default is 1)
      • Mark it as deprecated in mysqld --help output
      • Remove it in some later version, tentatively in 10.6.

      In the meanwhile, we should try to find proves that this problem was really addressed in Linux.

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              Assignee:
              bar Alexander Barkov
              Reporter:
              bar Alexander Barkov
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