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  1. MariaDB Server
  2. MDEV-25425

Useless message "If the mysqld execution user is authorized page cleaner thread priority can be changed."

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      Description

      On startup, InnoDB tries to prioritize the page cleaner thread. This usually fails, resulting in a log message like the following:

      Apr 15 03:28:17 ubuntu-focal-amd64 mariadbd[4875]: 2021-04-15  3:28:17 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
      

      A search for that message in this bug reporting system reveals many community user bugs. So, it seems that this code is almost never effective and can be removed:

      #ifdef UNIV_LINUX
        /* linux might be able to set different setting for each thread.
        worth to try to set high priority for the page cleaner thread */
        const pid_t tid= static_cast<pid_t>(syscall(SYS_gettid));
        setpriority(PRIO_PROCESS, tid, -20);
        if (getpriority(PRIO_PROCESS, tid) != -20)
          ib::info() << "If the mysqld execution user is authorized,"
                        " page cleaner thread priority can be changed."
                        " See the man page of setpriority().";
      #endif /* UNIV_LINUX */
      

      When this code was heavily refactored in MDEV-23855, the throughput and latency were greatly improved even when the buf_flush_page_cleaner thread always ran the same priority with other threads in our benchmarks.

      So, this code should have no benefit in MariaDB Server 10.5.7 or later.

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              Assignee:
              marko Marko Mäkelä
              Reporter:
              marko Marko Mäkelä
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