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  1. MariaDB Server
  2. MDEV-27848

Remove unused wait/io/file/innodb/innodb_log_file

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      The performance_schema counter wait/io/file/innodb/innodb_log_file is always reported as 0.

      The way how redo log writes are being waited for was refactored in MDEV-21534, which is when the uninstrumented flush_lock and write_lock were introduced. Even before this change, all the wait/io/file/innodb/ counters were always 0 in my tests. I tested the latest 10.2 yesterday.

      Moreover, if the PMEM interface that was introduced in MDEV-17084 is being used, writes to the InnoDB log file will completely avoid any system calls and performance_schema instrumentation. The PMEM interface was rewritten in MDEV-14425 to cover also reads (during recovery).

      In MDEV-26603 we plan to implement asynchronous writes for the redo log.

      When it comes to persistent data files (wait/io/file/innodb/innodb_data_file) and the temporary data file (wait/io/file/innodb/innodb_temp_file), all writes are already since MDEV-23855 asynchronous and thus uninstrumented by performance_schema. Only page reads on a buffer pool miss would be synchronous and thus theoretically coverable by performance_schema. But, this ticket is only about removing the ib_logfile0 redo log file instrumentation.

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              Assignee:
              marko Marko Mäkelä
              Reporter:
              marko Marko Mäkelä
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