MDEV-16264 Use threadpool for Innodb background work.

Almost all threads have gone
- the "ticking" threads, that sleep a while then do some work)
(srv_monitor_thread, srv_error_monitor_thread, srv_master_thread)
were replaced with timers. Some timers are periodic,
e.g the "master" timer.

- The btr_defragment_thread is also replaced by a timer , which
reschedules it self when current defragment "item" needs throttling

- the buf_resize_thread and buf_dump_threads are substitutes with tasks
Ditto with page cleaner workers.

- purge workers threads are not tasks as well, and purge cleaner
coordinator is a combination of a task and timer.

- All AIO is outsourced to tpool, Innodb just calls thread_pool::submit_io()
and provides the callback.

- The srv_slot_t was removed, and innodb_debug_sync used in purge
is currently not working, and needs reimplementation.

1 files changed, 2 insertions, 12 deletions

diff --git a/storage/innobase/include/trx0purge.h b/storage/innobase/include/trx0purge.h
index 7c3343ce7d2..9f3438b7f7d 100644
--- a/storage/innobase/include/trx0purge.h
+++ b/storage/innobase/include/trx0purge.h
@@ -62,10 +62,6 @@ trx_purge(
 	ulint	n_purge_threads,	/*!< in: number of purge tasks to
 					submit to task queue. */
 	bool	truncate		/*!< in: truncate history if true */
-#ifdef UNIV_DEBUG
-	, srv_slot_t *slot		/*!< in/out: purge coordinator
-					thread slot */
-#endif
 );
 
 /** Rollback segements from a given transaction with trx-no
@@ -144,14 +140,11 @@ private:
 class purge_sys_t
 {
 public:
-	/** signal state changes; os_event_reset() and os_event_set()
-	are protected by rw_lock_x_lock(latch) */
-	MY_ALIGNED(CACHE_LINE_SIZE)
-	os_event_t	event;
 	/** latch protecting view, m_enabled */
 	MY_ALIGNED(CACHE_LINE_SIZE)
 	rw_lock_t	latch;
 private:
+	bool m_initialized;
 	/** whether purge is enabled; protected by latch and std::atomic */
 	std::atomic<bool>		m_enabled;
 	/** number of pending stop() calls without resume() */
@@ -162,9 +155,6 @@ public:
 	MY_ALIGNED(CACHE_LINE_SIZE)
 	ReadView	view;		/*!< The purge will not remove undo logs
 					which are >= this view (purge view) */
-	/** Number of not completed tasks. Accessed by srv_purge_coordinator
-	and srv_worker_thread by std::atomic. */
-	std::atomic<ulint>	n_tasks;
 
 	/** Iterator to the undo log records of committed transactions */
 	struct iterator
@@ -234,7 +224,7 @@ public:
     uninitialised. Real initialisation happens in create().
   */
 
-  purge_sys_t() : event(NULL), m_enabled(false), n_tasks(0) {}
+  purge_sys_t():m_initialized(false),m_enabled(false) {}
 
 
   /** Create the instance */