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  1. Documentation
  2. DOCS-3177

The per-database RW-lock is not yielded when searching an index

    • Type: Icon: Task Task
    • Resolution: Done
    • Priority: Icon: Minor - P4 Minor - P4
    • v1.3.7
    • Affects Version/s: None
    • Component/s: manual
    • None

      The docs at http://smalldatum.blogspot.com/2014/04/mongodb-tokumx-and-innodb-for-disk-io_15.html were not clear to me on three issues:
      1) the per-db RW-lock is not yielded from page faults while searching an index.
      2) this is only done for "predicted page faults", not real page faults. And I am not suggesting that it should be done on real page faults.
      3) a pending write lock request prevents new read requests when the per-db RW-lock is currently locked in read-mode. The FAQ states that W has precedence over read but I think that you should also mention this behavior.

      See http://smalldatum.blogspot.com/2014/04/mongodb-tokumx-and-innodb-for-disk-io_15.html for performance results and a brief description of the code.

            sam.kleinman Sam Kleinman (Inactive)
            mdcallag Mark Callaghan
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              10 years, 4 weeks, 2 days ago