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  1. MariaDB Server
  2. MDEV-22871

Contention on the buf_pool.page_hash

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      MDEV-15053 reduced some buf_pool.mutex contention, shifting some contention to the buf_pool.page_hash latches.

      MDEV-22850 removed some genuine contention on the latches by reducing the X-latch hold time.

      But, based on earlier perf record analysis we seem to have some spurious contention on concurrent S-latch requests. I believe that this is due to the spin loop rw_lock_lock_word_decr() that rw_lock_s_lock() is executing.

      Spurious S-latch conflicts could be addressed by implementing a bare-bones variant of rw-locks using std::atomic::fetch_add() for the S-latch and compare_exchange_strong() for the X-latch acquisition. This variant would not need to support any recursive latches at all.

      As far as I understand, only dict_index_t::lock, buf_block_t::lock, fil_space_t::latch, dict_sys.latch, purge_sys.latch may truly require some additional ‘bells and whistles’, such as recursive X-locks or SX-locks, instrumentation, and event-based wakeup of waiting requests.

      Most other types of InnoDB rw-locks should be held for extremely short durations only, and we might best implement both S and X latch acquisition with simple spin loops (inlined atomic operation possibly followed by a subroutine call for the spin loop).

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          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-19929 Add a startup message about PAUSE instruction timing

          • Major - Major loss of function.
          • In Review

          Bug - A problem which impairs or prevents the functions of the product. MDEV-21452 Use condition variables and normal mutexes instead of InnoDB os_event and mutex

          • Major - Major loss of function.
          • Closed
          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-23070 Duplicated counting of MONITOR_ADAPTIVE_HASH_ROW_ADDED

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-23369 False sharing in page_hash_latch::read_lock_wait()

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-23998 Race condition between buf_page_optimistic_get() and buf_page_t::init()

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-24271 rw_lock::read_lock_yield() may cause writer starvation

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-25815 mariabackup crash or debug assert with --backup --databases-exclude

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26033 Race condition between buf_pool.page_hash and buffer pool resizing

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

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26828 Spinning on buf_pool.page_hash is wasting CPU cycles

          • Major - Major loss of function.
          • Closed
          is blocked by

          Bug - A problem which impairs or prevents the functions of the product. MDEV-22877 Avoid unnecessary buf_pool.page_hash S-latch acquisition

          • Major - Major loss of function.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-24090 Optimize buf_page_optimistic_get()

          • Major - Major loss of function.
          • Open

          Task - A task that needs to be done. MDEV-26609 Avoid deriving ELEMENT_PER_LATCH from cacheline

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-26826 Duplicated computations of buf_pool.page_hash addresses

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-14659 Innodb scalibility issue found in Mariadb code for complex 'select' queries in Arm platform

          • Major - Major loss of function.
          • Closed

          Task - A task that needs to be done. MDEV-15053 Reduce buf_pool_t::mutex contention

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

          Bug - A problem which impairs or prevents the functions of the product. MDEV-22850 Reduce buf_pool.page_hash latch contention

          • Major - Major loss of function.
          • Closed

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              marko Marko Mäkelä
              marko Marko Mäkelä
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                Updated:
                Resolved:

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