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[Bug 1279671] Re: Upstream fix for http://bugs.mysql.com/bug.php?id=70768 causes RW lock creations and destructions at a high rate during ibuf merge

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** Bug watch added: MySQL Bug System #71708
   http://bugs.mysql.com/bug.php?id=71708

** Also affects: mysql-server via
   http://bugs.mysql.com/bug.php?id=71708
   Importance: Unknown
       Status: Unknown

** Description changed:

  MySQL 5.6.16 fixed http://bugs.mysql.com/bug.php?id=70768 by changing
  dict_table_t stat-related member locking. Instead of a static array of
  64 shared latches, to eliminate contention on these, each dict_table_t
  object got its own dynamically created and destroyed latch.
  
  The short-lived private dict_table_t objects such as those used in ibuf
  merge got these dynamic rwlatches too. Each (non-priority) rwlatch
  creation performs heap memory allocations, acquires rw_lock_list_mutex,
  creates two OS events, which in turn acquire os_sync_mutex.
  
  Parts of a Perf report on the preliminary PS-5.6.16 branch.
  
  -  14,88%  mysqld  mysqld               [.] ut_delay(unsigned long)
     - ut_delay(unsigned long)
        - 90,02% mutex_spin_wait(void*, bool, char const*, unsigned long)
           - 47,73% rw_lock_create_func(rw_lock_t*, char const*)
                dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
              + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
           - 46,52% rw_lock_free_func(rw_lock_t*)            - dict_mem_table_free(dict_table_t*)
                 + 92,34% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                 + 6,54% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + 1,11% ibuf_rec_get_volume_func(unsigned char const*)
  ...
  -   6,35%  mysqld  libpthread-2.12.so   [.] pthread_mutex_lock
     - pthread_mutex_lock
        - 35,31% os_event_create()
           - 60,64% rw_lock_create_func(rw_lock_t*, char const*)
                dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
              + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
           - 39,36% mutex_create_func(ib_mutex_t*, char const*)
                dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
              + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
        - 19,28% sync_array_reserve_cell(sync_array_t*, void*, unsigned long, char const*, unsigned long, unsigned long*)
           - 99,16% mutex_spin_wait(void*, bool, char const*, unsigned long)
              - 50,51% rw_lock_create_func(rw_lock_t*, char const*)
                   dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
              - 49,26% rw_lock_free_func(rw_lock_t*)
                 - dict_mem_table_free(dict_table_t*)
                    + 92,81% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                    + 6,48% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                    + 0,71% ibuf_rec_get_volume_func(unsigned char const*)
           + 0,82% rw_lock_s_lock_spin(void*, unsigned long, bool, bool, char const*, unsigned long)
        - 18,17% os_fast_mutex_free_func(pthread_mutex_t*)
           - 67,53% os_event_free(os_event*)
              - 59,21% rw_lock_free_func(rw_lock_t*)
                 - dict_mem_table_free(dict_table_t*)
                    + 91,27% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                    + 6,96% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                    + 1,77% ibuf_rec_get_volume_func(unsigned char const*)
              - 40,79% mutex_free_func(ib_mutex_t*)
                 - dict_mem_table_free(dict_table_t*)
                    + 91,62% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                    + 6,85% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                    + 1,53% ibuf_rec_get_volume_func(unsigned char const*)
           - 32,47% dict_mem_index_free(dict_index_t*)
              + 89,70% ibuf_dummy_index_free(dict_index_t*)
              + 8,57% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
              + 1,73% ibuf_rec_get_volume_func(unsigned char const*)
        - 7,98% os_event_free(os_event*)
           - 53,98% rw_lock_free_func(rw_lock_t*)
              - dict_mem_table_free(dict_table_t*)
                 + 91,23% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                 + 7,07% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + 1,69% ibuf_rec_get_volume_func(unsigned char const*)
           - 46,02% mutex_free_func(ib_mutex_t*)
              - dict_mem_table_free(dict_table_t*)
                 + 91,32% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                 + 6,99% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + 1,69% ibuf_rec_get_volume_func(unsigned char const*)
        - 7,17% sync_array_wait_event(sync_array_t*, unsigned long)
           - 98,83% mutex_spin_wait(void*, bool, char const*, unsigned long)
              - 50,14% rw_lock_create_func(rw_lock_t*, char const*)
                   dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
              - 49,35% rw_lock_free_func(rw_lock_t*)
                 - dict_mem_table_free(dict_table_t*)
                    + 92,97% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                    + 6,19% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                    + 0,84% ibuf_rec_get_volume_func(unsigned char const*)
           + 1,14% rw_lock_s_lock_spin(void*, unsigned long, bool, bool, char const*, unsigned long)
        - 6,76% os_fast_mutex_init_func(pthread_mutex_t*)
             dict_mem_index_create(char const*, char const*, unsigned long, unsigned long, unsigned long)
           + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
        - 3,89% mutex_signal_object(ib_mutex_t*)
           - 81,44% rw_lock_free_func(rw_lock_t*)
              - dict_mem_table_free(dict_table_t*)
                 + 92,90% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                 + 6,37% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + 0,73% ibuf_rec_get_volume_func(unsigned char const*)
           - 18,19% rw_lock_create_func(rw_lock_t*, char const*)
                dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
              + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
        - 0,76% sync_array_free_cell(sync_array_t*, unsigned long)
           - 87,03% mutex_spin_wait(void*, bool, char const*, unsigned long)
              - 50,19% rw_lock_create_func(rw_lock_t*, char const*)
                   dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
                 + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
              - 46,32% rw_lock_free_func(rw_lock_t*)
                 - dict_mem_table_free(dict_table_t*)
                    + 93,59% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
                    + 5,77% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
                    + 0,64% ibuf_rec_get_volume_func(unsigned char const*)
              + 1,88% pfs_mutex_enter_func(ib_mutex_t*, char const*, unsigned long)
              + 0,87% mtr_commit(mtr_t*)
              + 0,53% _ZL20pfs_mutex_enter_funcP10ib_mutex_tPKcm.clone.2
           + 12,46% rw_lock_s_lock_spin(void*, unsigned long, bool, bool, char const*, unsigned long)
  -   3,68%  mysqld  mysqld               [.] mutex_spin_wait(void*, bool, char const*, unsigned long)
     - mutex_spin_wait(void*, bool, char const*, unsigned long)
        - 48,40% rw_lock_create_func(rw_lock_t*, char const*)
             dict_mem_table_create(char const*, unsigned long, unsigned long, unsigned long, unsigned long)
           + ibuf_build_entry_from_ibuf_rec_func(unsigned char const*, mem_block_info_t*, dict_index_t**)
        - 46,88% rw_lock_free_func(rw_lock_t*)
           - dict_mem_table_free(dict_table_t*)
              + 92,22% _ZL35ibuf_get_volume_buffered_count_funcPKhPmmPl.clone.0
              + 6,71% ibuf_merge_or_delete_for_page(buf_block_t*, unsigned long, unsigned long, unsigned long, unsigned long)
              + 1,07% ibuf_rec_get_volume_func(unsigned char const*)
  
  The above causes a performance regression on MySQL 5.6.16 merge in TPS
  of RW Sysbench (I/O bound (!)): about 7% drop at 512 threads, 20% at
  1024 threads.
- 
- Upstream bug report pending.

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https://bugs.launchpad.net/bugs/1279671

Title:
  Upstream fix for http://bugs.mysql.com/bug.php?id=70768 causes RW lock
  creations and destructions at a high rate during ibuf merge

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