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  1. MariaDB Server
  2. MDEV-13670

[Note] InnoDB: page_cleaner: 1000ms intended loop took XXXXms. The settings might not be optimal. (flushed=0 and evicted=0, during the time.)

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      Hi,
      I migrated from MySQL 5.6.36 to MariaDB 10.2.8 32bit on Windows 2008 R1.
      I have started to see the following in our production environment.

      2017-08-29 10:45:24 4432 [Note] InnoDB: page_cleaner: 1000ms intended loop took 4197ms. The settings might not be optimal. (flushed=0 and evicted=0, during the time.)
      

      I have not made any changes to the configuration file (my.ini); I was wondering do I need to

      the settings are:-

      MariaDB [(none)]> show global variables like 'innodb_buffer%';
      +-------------------------------------+----------------+
      | Variable_name                       | Value          |
      +-------------------------------------+----------------+
      | innodb_buffer_pool_chunk_size       | 134217728      |
      | innodb_buffer_pool_dump_at_shutdown | ON             |
      | innodb_buffer_pool_dump_now         | OFF            |
      | innodb_buffer_pool_dump_pct         | 25             |
      | innodb_buffer_pool_filename         | ib_buffer_pool |
      | innodb_buffer_pool_instances        | 1              |
      | innodb_buffer_pool_load_abort       | OFF            |
      | innodb_buffer_pool_load_at_startup  | ON             |
      | innodb_buffer_pool_load_now         | OFF            |
      | innodb_buffer_pool_populate         | OFF            |
      | innodb_buffer_pool_size             | 268435456      |
      +-------------------------------------+----------------+
      11 rows in set (0.00 sec)
      

      Do I need to increase innodb_buffer_pool_instances, or anything else to stop this latency which I never saw logged with MySQL 5.6.36?

      many thanks for your advice and guidance.

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            This change originated from MySQL 5.7, which MariaDB’s InnoDB implementation is based on.
            One of the first reports of this is Bug #75846 page_cleaner thread configuration warning spams error log on laptops,
            filed one month after the message was introduced in MySQL 5.7.6.

            The suggestion to omit this message when both reported counts are 0 might make sense.
            The reporter also mentioned a related request: Bug #71662 InnoDB background threads should be configurable to reduce power consumption.

            marko Marko Mäkelä added a comment - This change originated from MySQL 5.7, which MariaDB’s InnoDB implementation is based on. One of the first reports of this is Bug #75846 page_cleaner thread configuration warning spams error log on laptops , filed one month after the message was introduced in MySQL 5.7.6 . The suggestion to omit this message when both reported counts are 0 might make sense. The reporter also mentioned a related request: Bug #71662 InnoDB background threads should be configurable to reduce power consumption .

            Setting to Confirmed based on the comment above.

            elenst Elena Stepanova added a comment - Setting to Confirmed based on the comment above.

            Marko wants to at some point understand exactly why we get this error and what we can do to
            avoid warnings that the user can't do anything about.

            In the mean time, we will change so that this warning is only given if log_warnings is 3 or above.

            monty Michael Widenius added a comment - Marko wants to at some point understand exactly why we get this error and what we can do to avoid warnings that the user can't do anything about. In the mean time, we will change so that this warning is only given if log_warnings is 3 or above.

            Marko has now committed in 10.2 tree a fix that we don't write the page_cleaner information if log_warnings is 2 or less

            monty Michael Widenius added a comment - Marko has now committed in 10.2 tree a fix that we don't write the page_cleaner information if log_warnings is 2 or less

            The message was hidden at the default log_warnings level (2 or less). The actual problem will be addressed in MDEV-16526.

            marko Marko Mäkelä added a comment - The message was hidden at the default log_warnings level (2 or less). The actual problem will be addressed in MDEV-16526 .

            Until MDEV-23399, the ‘flush_list flushing batch’ would actually wait for buffer pool page latches, and therefore a single batch can take an arbitrarily long time.

            marko Marko Mäkelä added a comment - Until MDEV-23399 , the ‘flush_list flushing batch’ would actually wait for buffer pool page latches, and therefore a single batch can take an arbitrarily long time.

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              marko Marko Mäkelä
              slaterss Stuart Slater
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