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[Laurynas Biveinis <laurynas.biveinis@xxxxxxxxx>]

Public bug reported:

Copy of https://bugs.mysql.com/bug.php?id=79894:

[8 Jan 13:56] Laurynas Biveinis
Description:
Credit shared with Alexey Stroganov.

Page cleaner worker threads do not call pfs_register_thread.

This means:
1) (if I recall correctly how PFS thread instrumentation works) no events by these threads are actually accounted.
2) they are invisible in PERFORMANCE_SCHEMA.THREADS table.

If 1) is correct, then any results so far on 5.7 to gain insights into
MT page cleaner performance by PFS are basically invalid. To verify 2),
start server in default configuration, and query P_S.THREADS. You will
see one cleaner thread there only. The three worker threads there are
purge. The cleaner worker threads are not there.

How to repeat:
See above, check buf0flu.cc for buf_flush_page_cleaner_worker NOT calling pfs_register_thread.

Suggested fix:
Add a new thread key, register cleaner worker threads with PFS.

** Affects: mysql-server
     Importance: Unknown
         Status: Unknown

** Affects: percona-server
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.1
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.5
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.6
     Importance: Undecided
         Status: Invalid

** Affects: percona-server/5.7
     Importance: Medium
     Assignee: Laurynas Biveinis (laurynas-biveinis)
         Status: Triaged


** Tags: performance upstream

** Also affects: percona-server/5.6
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.7
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.1
   Importance: Undecided
       Status: New

** Also affects: percona-server/5.5
   Importance: Undecided
       Status: New

** Changed in: percona-server/5.1
       Status: New => Invalid

** Changed in: percona-server/5.5
       Status: New => Invalid

** Changed in: percona-server/5.6
       Status: New => Invalid

** Changed in: percona-server/5.7
       Status: New => Triaged

** Changed in: percona-server/5.7
   Importance: Undecided => Medium

** Changed in: percona-server/5.7
     Assignee: (unassigned) => Laurynas Biveinis (laurynas-biveinis)

** Tags added: performance upstream

** Bug watch added: MySQL Bug System #79894
   http://bugs.mysql.com/bug.php?id=79894

** Also affects: mysql-server via
   http://bugs.mysql.com/bug.php?id=79894
   Importance: Unknown
       Status: Unknown

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https://bugs.launchpad.net/bugs/1532747

Title:
  Page cleaner worker threads are not instrumented for performance
  schema

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