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  1. MariaDB Server
  2. MDEV-6614

Merge InnoDB: fix index->lock contention from MySQL 5.7

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      Description

      revno: 6232 
      revno: 6233
      revno: 6902
        - WL#6326 : InnoDB: fix index->lock contention

      The acquisition of node pointer page latches is protected by index->lock latch.Currently, index->lock protected all node pointer pages either in S or X mode, and no individual block->lock were acquired on node pointer pages. With this fix, node pointer pages are protected by individual block->lock, S-latch or X-latch. The acquisition of node pointer page latches is covered by index->lock, for preventing deadlocks.

      InnoDB internally uses rw-lock implementation to keep consistency of internal
      resources. Basically the rw-lock has 2 types S-lock (shared) and X-lock (exluded).
      The fix adds the new type SX-lock (shared excluded) for room to optimize
      concurrency and improve scalability more.

      At least, S-lock and X-lock behave same, and compatible for current code. So,
      nothing changed by only this fix as it is. (no functional/performance changes
      for users)

      The new state SX-lock will be used by the future work. (e.g. WL#6326: InnoDB:
      fix index->lock contention)

        new state of rw_lock: SX-lock
              | S|SX| X|
            --+--+--+--+
             S| o| o| x|
            --+--+--+--+
            SX| o| x| x|
            --+--+--+--+
             X| x| x| x|
            --+--+--+--+
        

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              • Assignee:
                jplindst Jan Lindström
                Reporter:
                jplindst Jan Lindström
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                • Created:
                  Updated:
                  Resolved: