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  1. MariaDB Server
  2. MDEV-39401

Buffer AHI usage counters btr_cur_n_*sea in non-atomic members of trx_t

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      AHI usage counters, btr_cur_n_sea and btr_cur_n_non_sea, incremented in btr_cur_t::search_leaf(), are global instances of ib_counter_t<ulint, ib_counter_element_t>, which is a sharded (size 128) non-atomic (fuzzy) counter.

      The usage of such a peculiar data type might suggest earlier attempts at overhead reduction for incrementing those two counters.

      A better solution indicated by marko would be to replicate what was done in MDEV-37152: move the counters to some non-atomic members of trx_t and apply those changes back to the global counters (they can be possibly atomic then) only once per transaction (check trx_t::pages_accessed).

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-21212 buf_page_get_gen -> buf_pool->stat.n_page_gets++ is a cpu waste (0.5-1%)

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          New Feature - A new feature of the product, which has yet to be developed. MDEV-37070 Implement table options to enable/disable features

          • Critical - Crashes, loss of data, severe memory leak.
          • Stalled

          Bug - A problem which impairs or prevents the functions of the product. MDEV-37152 buf_page_get_gen -> buf_pool->stat.n_page_gets++ high cpu utilisation

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          New Feature - A new feature of the product, which has yet to be developed. MDEV-38305 Expose adaptive hash index statistics in ANALYZE FORMAT=JSON

          • Major - Major loss of function.
          • Open

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              Unassigned Unassigned
              alessandro.vetere Alessandro Vetere
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