MDEV-19313 Threadpool : provide information schema tables for internals of generic threadpool

Added thread_pool_groups, thread_pool_queues, thread_pool_waits and
thread_pool_stats tables to information_schema.

sql/CMakeLists.txt

@@ -164,6 +164,7 @@ IF ((CMAKE_SYSTEM_NAME MATCHES "Linux" OR
  ENDIF()
  SET(SQL_SOURCE ${SQL_SOURCE} threadpool_generic.cc)
  SET(SQL_SOURCE ${SQL_SOURCE} threadpool_common.cc)
+ MYSQL_ADD_PLUGIN(thread_pool_info thread_pool_info.cc DEFAULT STATIC_ONLY NOT_EMBEDDED)
 ENDIF()
 
 IF(WIN32)

sql/mysqld.cc

@@ -7461,7 +7461,7 @@ static int debug_status_func(THD *thd, SHOW_VAR *var, char *buff,
 #endif
 
 #ifdef HAVE_POOL_OF_THREADS
-int show_threadpool_idle_threads(THD *thd, SHOW_VAR *var, char *buff,
+static int show_threadpool_idle_threads(THD *thd, SHOW_VAR *var, char *buff,
                                  enum enum_var_type scope)
 {
   var->type= SHOW_INT;

sql/thread_pool_info.cc

+/* Copyright(C) 2019 MariaDB
+
+This program is free software; you can redistribute itand /or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 - 1301 USA*/
+
+#include <mysql_version.h>
+#include <mysql/plugin.h>
+
+#include <my_global.h>
+#include <sql_class.h>
+#include <table.h>
+#include <mysql/plugin.h>
+#include <sql_show.h>
+#include <threadpool_generic.h>
+
+static ST_FIELD_INFO groups_fields_info[] =
+{
+  {"GROUP_ID", 6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"CONNECTIONS", 6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"THREADS", 6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"ACTIVE_THREADS",6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"STANDBY_THREADS", 6, MYSQL_TYPE_LONG, 0, 0, 0,0},
+  {"QUEUE_LENGTH", 6, MYSQL_TYPE_LONG, 0,0, 0, 0},
+  {"HAS_LISTENER",1,MYSQL_TYPE_TINY, 0, 0, 0, 0},
+  {"IS_STALLED",1,MYSQL_TYPE_TINY, 0, 0, 0, 0},
+  {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, 0}
+};
+
+static int groups_fill_table(THD* thd, TABLE_LIST* tables, COND*)
+{
+  if (!all_groups)
+    return 0;
+
+  TABLE* table = tables->table;
+  for (uint i = 0; i < threadpool_max_size && all_groups[i].pollfd != INVALID_HANDLE_VALUE; i++)
+  {
+    thread_group_t* group = &all_groups[i];
+    /* ID */
+    table->field[0]->store(i, true);
+    /* CONNECTION_COUNT */
+    table->field[1]->store(group->connection_count, true);
+    /* THREAD_COUNT */
+    table->field[2]->store(group->thread_count, true);
+    /* ACTIVE_THREAD_COUNT */
+    table->field[3]->store(group->active_thread_count, true);
+    /* STANDBY_THREAD_COUNT */
+    table->field[4]->store(group->waiting_threads.elements(), true);
+    /* QUEUE LENGTH */
+    uint queue_len = group->queues[TP_PRIORITY_LOW].elements()
+      + group->queues[TP_PRIORITY_HIGH].elements();
+    table->field[5]->store(queue_len, true);
+    /* HAS_LISTENER */
+    table->field[6]->store((longlong)(group->listener != 0), true);
+    /* IS_STALLED */
+    table->field[7]->store(group->stalled, true);
+
+    if (schema_table_store_record(thd, table))
+      return 1;
+  }
+  return 0;
+}
+
+
+static int groups_init(void* p)
+{
+  ST_SCHEMA_TABLE* schema = (ST_SCHEMA_TABLE*)p;
+  schema->fields_info = groups_fields_info;
+  schema->fill_table = groups_fill_table;
+  return 0;
+}
+
+
+static ST_FIELD_INFO queues_field_info[] =
+{
+  {"GROUP_ID", 6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"POSITION",6,MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"PRIORITY", 1, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"CONNECTION_ID", 19, MYSQL_TYPE_LONGLONG, MY_I_S_UNSIGNED, 0, 0, 0},
+  {"QUEUEING_TIME_MICROSECONDS", 19, MYSQL_TYPE_LONGLONG, 0, 0, 0, 0},
+  {0, 0, MYSQL_TYPE_NULL, 0, 0, 0, 0}
+};
+
+typedef connection_queue_t::Iterator connection_queue_iterator;
+
+static int queues_fill_table(THD* thd, TABLE_LIST* tables, COND*)
+{
+  if (!all_groups)
+    return 0;
+
+  TABLE* table = tables->table;
+  for (uint group_id = 0;
+    group_id < threadpool_max_size && all_groups[group_id].pollfd != INVALID_HANDLE_VALUE;
+    group_id++)
+  {
+    thread_group_t* group = &all_groups[group_id];
+
+    mysql_mutex_lock(&group->mutex);
+    bool err = false;
+    int pos = 0;
+    ulonglong now = microsecond_interval_timer();
+    for (uint prio = 0; prio < NQUEUES && !err; prio++)
+    {
+      connection_queue_iterator it(group->queues[prio]);
+      TP_connection_generic* c;
+      while ((c = it++) != 0)
+      {
+        /* GROUP_ID */
+        table->field[0]->store(group_id, true);
+        /* POSITION */
+        table->field[1]->store(pos++, true);
+        /* PRIORITY */
+        table->field[2]->store(prio, true);
+        /* CONNECTION_ID */
+        table->field[3]->store(c->thd->thread_id, true);
+        /* QUEUEING_TIME */
+        table->field[4]->store(now - c->enqueue_time, true);
+
+        err = schema_table_store_record(thd, table);
+        if (err)
+          break;
+      }
+    }
+    mysql_mutex_unlock(&group->mutex);
+    if (err)
+      return 1;
+  }
+  return 0;
+}
+
+static int queues_init(void* p)
+{
+  ST_SCHEMA_TABLE* schema = (ST_SCHEMA_TABLE*)p;
+  schema->fields_info = queues_field_info;
+  schema->fill_table = queues_fill_table;
+  return 0;
+}
+
+static ST_FIELD_INFO stats_fields_info[] =
+{
+  {"GROUP_ID", 6, MYSQL_TYPE_LONG, 0, 0, 0, 0},
+  {"THREAD_CREATIONS",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {"THREAD_CREATIONS_DUE_TO_STALL",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {"WAKES",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {"WAKES_DUE_TO_STALL",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {"THROTTLES",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {"STALLS",19,MYSQL_TYPE_LONGLONG,0,0, 0, 0},
+  {"POLLS_BY_LISTENER",19,MYSQL_TYPE_LONGLONG,0,0, 0, 0},
+  {"POLLS_BY_WORKER",19,MYSQL_TYPE_LONGLONG,0,0, 0, 0},
+  {"DEQUEUES_BY_LISTENER",19,MYSQL_TYPE_LONGLONG,0,0, 0, 0},
+  {"DEQUEUES_BY_WORKER",19,MYSQL_TYPE_LONGLONG,0,0, 0, 0},
+  {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, 0}
+};
+
+static int stats_fill_table(THD* thd, TABLE_LIST* tables, COND*)
+{
+  if (!all_groups)
+    return 0;
+
+  TABLE* table = tables->table;
+  for (uint i = 0; i < threadpool_max_size && all_groups[i].pollfd != INVALID_HANDLE_VALUE; i++)
+  {
+    table->field[0]->store(i, true);
+    thread_group_t* group = &all_groups[i];
+
+    mysql_mutex_lock(&group->mutex);
+    thread_group_counters_t* counters = &group->counters;
+    table->field[1]->store(counters->thread_creations, true);
+    table->field[2]->store(counters->thread_creations_due_to_stall, true);
+    table->field[3]->store(counters->wakes, true);
+    table->field[4]->store(counters->wakes_due_to_stall, true);
+    table->field[5]->store(counters->throttles, true);
+    table->field[6]->store(counters->stalls, true);
+    table->field[7]->store(counters->polls_by_listener, true);
+    table->field[8]->store(counters->polls_by_worker, true);
+    table->field[9]->store(counters->dequeues_by_listener, true);
+    table->field[10]->store(counters->dequeues_by_worker, true);
+    mysql_mutex_unlock(&group->mutex);
+    if (schema_table_store_record(thd, table))
+      return 1;
+  }
+  return 0;
+}
+
+static int stats_reset_table()
+{
+  for (uint i = 0; i < threadpool_max_size && all_groups[i].pollfd != INVALID_HANDLE_VALUE; i++)
+  {
+    thread_group_t* group = &all_groups[i];
+    mysql_mutex_lock(&group->mutex);
+    memset(&group->counters, 0, sizeof(group->counters));
+    mysql_mutex_unlock(&group->mutex);
+  }
+  return 0;
+}
+
+static int stats_init(void* p)
+{
+  ST_SCHEMA_TABLE* schema = (ST_SCHEMA_TABLE*)p;
+  schema->fields_info = stats_fields_info;
+  schema->fill_table = stats_fill_table;
+  schema->reset_table = stats_reset_table;
+  return 0;
+}
+
+
+
+static ST_FIELD_INFO waits_fields_info[] =
+{
+  {"REASON", 16, MYSQL_TYPE_STRING, 0, 0, 0, 0},
+  {"COUNT",19,MYSQL_TYPE_LONGLONG,0,0, 0,0},
+  {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, 0}
+};
+
+/* See thd_wait_type enum for explanation*/
+static const LEX_CSTRING wait_reasons[THD_WAIT_LAST] =
+{
+  {STRING_WITH_LEN("UNKNOWN")},
+  {STRING_WITH_LEN("SLEEP")},
+  {STRING_WITH_LEN("DISKIO")},
+  {STRING_WITH_LEN("ROW_LOCK")},
+  {STRING_WITH_LEN("GLOBAL_LOCK")},
+  {STRING_WITH_LEN("META_DATA_LOCK")},
+  {STRING_WITH_LEN("TABLE_LOCK")},
+  {STRING_WITH_LEN("USER_LOCK")},
+  {STRING_WITH_LEN("BINLOG")},
+  {STRING_WITH_LEN("GROUP_COMMIT")},
+  {STRING_WITH_LEN("SYNC")},
+  {STRING_WITH_LEN("NET")}
+};
+
+extern Atomic_counter<unsigned long long> tp_waits[THD_WAIT_LAST];
+
+static int waits_fill_table(THD* thd, TABLE_LIST* tables, COND*)
+{
+  if (!all_groups)
+    return 0;
+
+  TABLE* table = tables->table;
+  for (auto i = 0; i < THD_WAIT_LAST; i++)
+  {
+    table->field[0]->store(wait_reasons[i].str, wait_reasons[i].length, system_charset_info);
+    table->field[1]->store(tp_waits[i], true);
+    if (schema_table_store_record(thd, table))
+      return 1;
+  }
+  return 0;
+}
+
+static int waits_reset_table()
+{
+  for (auto i = 0; i < THD_WAIT_LAST; i++)
+    tp_waits[i] = 0;
+
+  return 0;
+}
+
+static int waits_init(void* p)
+{
+  ST_SCHEMA_TABLE* schema = (ST_SCHEMA_TABLE*)p;
+  schema->fields_info = waits_fields_info;
+  schema->fill_table = waits_fill_table;
+  schema->reset_table = waits_reset_table;
+  return 0;
+}
+
+static struct st_mysql_information_schema plugin_descriptor =
+{ MYSQL_INFORMATION_SCHEMA_INTERFACE_VERSION };
+
+maria_declare_plugin(thread_pool_info)
+{
+  MYSQL_INFORMATION_SCHEMA_PLUGIN,
+  &plugin_descriptor,
+  "THREAD_POOL_GROUPS",
+  "Vladislav Vaintroub",
+  "Provides information about threadpool groups.",
+  PLUGIN_LICENSE_GPL,
+  groups_init,
+  0,
+  0x0100,
+  NULL,
+  NULL,
+  "1.0",
+  MariaDB_PLUGIN_MATURITY_STABLE
+},
+{
+  MYSQL_INFORMATION_SCHEMA_PLUGIN,
+  &plugin_descriptor,
+  "THREAD_POOL_QUEUES",
+  "Vladislav Vaintroub",
+  "Provides information about threadpool queues.",
+  PLUGIN_LICENSE_GPL,
+  queues_init,
+  0,
+  0x0100,
+  NULL,
+  NULL,
+  "1.0",
+  MariaDB_PLUGIN_MATURITY_STABLE
+},
+{
+  MYSQL_INFORMATION_SCHEMA_PLUGIN,
+  &plugin_descriptor,
+  "THREAD_POOL_STATS",
+  "Vladislav Vaintroub",
+  "Provides performance counter information for threadpool.",
+  PLUGIN_LICENSE_GPL,
+  stats_init,
+  0,
+  0x0100,
+  NULL,
+  NULL,
+  "1.0",
+  MariaDB_PLUGIN_MATURITY_STABLE
+},
+{
+  MYSQL_INFORMATION_SCHEMA_PLUGIN,
+  &plugin_descriptor,
+  "THREAD_POOL_WAITS",
+  "Vladislav Vaintroub",
+  "Provides wait counters for threadpool.",
+  PLUGIN_LICENSE_GPL,
+  waits_init,
+  0,
+  0x0100,
+  NULL,
+  NULL,
+  "1.0",
+  MariaDB_PLUGIN_MATURITY_STABLE
+}
+maria_declare_plugin_end;

sql/threadpool.h

@@ -64,8 +64,6 @@ extern int tp_get_thread_count();
 /* Activate threadpool scheduler */
 extern void tp_scheduler(void);
 
-extern int show_threadpool_idle_threads(THD *thd, SHOW_VAR *var, char *buff,
-                                        enum enum_var_type scope);
 
 enum  TP_PRIORITY {
   TP_PRIORITY_HIGH,
@@ -88,6 +86,8 @@ enum TP_STATE
   inside threadpool_win.cc and threadpool_unix.cc
 */
 
+class CONNECT;
+
 struct TP_connection
 {
   THD*        thd;

sql/threadpool_common.cc

@@ -23,7 +23,7 @@
 #include <sql_audit.h>
 #include <debug_sync.h>
 #include <threadpool.h>
-
+#include <my_counter.h>
 
 /* Threadpool parameters */
 
@@ -153,9 +153,8 @@ static TP_PRIORITY get_priority(TP_connection *c)
   DBUG_ASSERT(c->thd == current_thd);
   TP_PRIORITY prio= (TP_PRIORITY)c->thd->variables.threadpool_priority;
   if (prio == TP_PRIORITY_AUTO)
-  {
-    return c->thd->transaction.is_active() ? TP_PRIORITY_HIGH : TP_PRIORITY_LOW;
-  }
+    prio= c->thd->transaction.is_active() ? TP_PRIORITY_HIGH : TP_PRIORITY_LOW;
+
   return prio;
 }
 
@@ -463,12 +462,17 @@ void tp_timeout_handler(TP_connection *c)
   mysql_mutex_unlock(&thd->LOCK_thd_kill);
 }
 
+MY_ALIGNED(CPU_LEVEL1_DCACHE_LINESIZE) Atomic_counter<unsigned long long> tp_waits[THD_WAIT_LAST];
 
 static void tp_wait_begin(THD *thd, int type)
 {
   TP_connection *c = get_TP_connection(thd);
   if (c)
+  {
+    DBUG_ASSERT(type > 0 && type < THD_WAIT_LAST);
+    tp_waits[type]++;
     c->wait_begin(type);
+  }
 }
 
 

sql/threadpool_generic.cc

@@ -13,56 +13,27 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */
 
+#if (defined HAVE_POOL_OF_THREADS) && !defined(EMBEDDED_LIBRARY)
+
+#include "threadpool_generic.h"
 #include "mariadb.h"
 #include <violite.h>
 #include <sql_priv.h>
 #include <sql_class.h>
 #include <my_pthread.h>
 #include <scheduler.h>
-
-#ifdef HAVE_POOL_OF_THREADS
-
-#ifdef _WIN32
-/* AIX may define this, too ?*/
-#define HAVE_IOCP 
-#endif
-
-#ifdef HAVE_IOCP
-#define OPTIONAL_IO_POLL_READ_PARAM this
-#else 
-#define OPTIONAL_IO_POLL_READ_PARAM 0
-#endif
-
-#ifdef _WIN32
-typedef HANDLE TP_file_handle;
-#else
-typedef int TP_file_handle;
-#define  INVALID_HANDLE_VALUE -1
-#endif
-
-
 #include <sql_connect.h>
 #include <mysqld.h>
 #include <debug_sync.h>
 #include <time.h>
 #include <sql_plist.h>
 #include <threadpool.h>
-#include <time.h>
-#ifdef __linux__
-#include <sys/epoll.h>
-typedef struct epoll_event native_event;
-#elif defined(HAVE_KQUEUE)
-#include <sys/event.h>
-typedef struct kevent native_event;
-#elif defined (__sun)
-#include <port.h>
-typedef port_event_t native_event;
-#elif defined (HAVE_IOCP)
-typedef OVERLAPPED_ENTRY native_event;
-#else
-#error threadpool is not available on this platform
-#endif
 
+#ifdef HAVE_IOCP
+#define OPTIONAL_IO_POLL_READ_PARAM this
+#else 
+#define OPTIONAL_IO_POLL_READ_PARAM 0
+#endif
 
 static void io_poll_close(TP_file_handle fd)
 {
@@ -119,86 +90,7 @@ static PSI_thread_info	thread_list[] =
 #define PSI_register(X) /* no-op */
 #endif
 
-
-struct thread_group_t;
-
-/* Per-thread structure for workers */
-struct worker_thread_t
-{
-  ulonglong  event_count; /* number of request handled by this thread */
-  thread_group_t* thread_group;   
-  worker_thread_t *next_in_list;
-  worker_thread_t **prev_in_list;
-  
-  mysql_cond_t  cond;
-  bool          woken;
-};
-
-typedef I_P_List<worker_thread_t, I_P_List_adapter<worker_thread_t,
-                 &worker_thread_t::next_in_list,
-                 &worker_thread_t::prev_in_list> 
-                 >
-worker_list_t;
-
-struct TP_connection_generic:public TP_connection
-{
-  TP_connection_generic(CONNECT *c);
-  ~TP_connection_generic();
- 
-  virtual int init(){ return 0; };
-  virtual void set_io_timeout(int sec);
-  virtual int  start_io();
-  virtual void wait_begin(int type);
-  virtual void wait_end();
-
-  thread_group_t *thread_group;
-  TP_connection_generic *next_in_queue;
-  TP_connection_generic **prev_in_queue;
-  ulonglong abs_wait_timeout;
-  ulonglong dequeue_time;
-  TP_file_handle fd;
-  bool bound_to_poll_descriptor;
-  int waiting;
-#ifdef HAVE_IOCP
-  OVERLAPPED overlapped;
-#endif
-#ifdef _WIN32
-  enum_vio_type vio_type;
-#endif
-};
-
-
-typedef I_P_List<TP_connection_generic,
-                     I_P_List_adapter<TP_connection_generic,
-                                      &TP_connection_generic::next_in_queue,
-                                      &TP_connection_generic::prev_in_queue>,
-                     I_P_List_null_counter,
-                     I_P_List_fast_push_back<TP_connection_generic> >
-connection_queue_t;
-
-const int NQUEUES=2; /* We have high and low priority queues*/
-
-struct MY_ALIGNED(CPU_LEVEL1_DCACHE_LINESIZE) thread_group_t
-{
-  mysql_mutex_t mutex;
-  connection_queue_t queues[NQUEUES];
-  worker_list_t waiting_threads; 
-  worker_thread_t *listener;
-  pthread_attr_t *pthread_attr;
-  TP_file_handle  pollfd;
-  int  thread_count;
-  int  active_thread_count;
-  int  connection_count;
-  /* Stats for the deadlock detection timer routine.*/
-  int io_event_count;
-  int queue_event_count;
-  ulonglong last_thread_creation_time;
-  int  shutdown_pipe[2];
-  bool shutdown;
-  bool stalled; 
-};
-
-static thread_group_t *all_groups;
+thread_group_t *all_groups;
 static uint group_count;
 static int32 shutdown_group_count;
 
@@ -224,9 +116,9 @@ static pool_timer_t pool_timer;
 
 static void queue_put(thread_group_t *thread_group, TP_connection_generic *connection);
 static void queue_put(thread_group_t *thread_group, native_event *ev, int cnt);
-static int  wake_thread(thread_group_t *thread_group);
-static int  wake_or_create_thread(thread_group_t *thread_group);
-static int  create_worker(thread_group_t *thread_group);
+static int  wake_thread(thread_group_t *thread_group,bool due_to_stall);
+static int  wake_or_create_thread(thread_group_t *thread_group, bool due_to_stall=false);
+static int  create_worker(thread_group_t *thread_group, bool due_to_stall);
 static void *worker_main(void *param);
 static void check_stall(thread_group_t *thread_group);
 static void set_next_timeout_check(ulonglong abstime);
@@ -563,11 +455,11 @@ static void queue_init(thread_group_t *thread_group)
 
 static void queue_put(thread_group_t *thread_group, native_event *ev, int cnt)
 {
-  ulonglong now= pool_timer.current_microtime;
+  ulonglong now= threadpool_exact_stats?microsecond_interval_timer():pool_timer.current_microtime;
   for(int i=0; i < cnt; i++)
   {
     TP_connection_generic *c = (TP_connection_generic *)native_event_get_userdata(&ev[i]);
-    c->dequeue_time= now;
+    c->enqueue_time= now;
     thread_group->queues[c->priority].push_back(c);
   }
 }
@@ -681,7 +573,7 @@ void check_stall(thread_group_t *thread_group)
   for (;;)
   {
     c= thread_group->queues[TP_PRIORITY_LOW].front();
-    if (c && pool_timer.current_microtime - c->dequeue_time > 1000ULL * threadpool_prio_kickup_timer)
+    if (c && pool_timer.current_microtime - c->enqueue_time > 1000ULL * threadpool_prio_kickup_timer)
     {
       thread_group->queues[TP_PRIORITY_LOW].remove(c);
       thread_group->queues[TP_PRIORITY_HIGH].push_back(c);
@@ -698,7 +590,7 @@ void check_stall(thread_group_t *thread_group)
   */
   if (!thread_group->listener && !thread_group->io_event_count)
   {
-    wake_or_create_thread(thread_group);
+    wake_or_create_thread(thread_group, true);
     mysql_mutex_unlock(&thread_group->mutex);
     return;
   }
@@ -735,7 +627,8 @@ void check_stall(thread_group_t *thread_group)
   if (!is_queue_empty(thread_group) && !thread_group->queue_event_count)
   {
     thread_group->stalled= true;
-    wake_or_create_thread(thread_group);
+    TP_INCREMENT_GROUP_COUNTER(thread_group,stalls);
+    wake_or_create_thread(thread_group,true);
   }
   
   /* Reset queue event count */
@@ -790,13 +683,13 @@ static TP_connection_generic * listener(worker_thread_t *current_thread,
       break;
   
     cnt = io_poll_wait(thread_group->pollfd, ev, MAX_EVENTS, -1);
-    
+    TP_INCREMENT_GROUP_COUNTER(thread_group, polls_by_listener);
     if (cnt <=0)
     {
       DBUG_ASSERT(thread_group->shutdown);
       break;
     }
-
+    
     mysql_mutex_lock(&thread_group->mutex);
 
     if (thread_group->shutdown)
@@ -864,7 +757,7 @@ static TP_connection_generic * listener(worker_thread_t *current_thread,
     if(thread_group->active_thread_count==0)
     {
       /* We added some work items to queue, now wake a worker. */
-      if(wake_thread(thread_group))
+      if(wake_thread(thread_group, false))
       {
         /* 
           Wake failed, hence groups has no idle threads. Now check if there are
@@ -882,7 +775,7 @@ static TP_connection_generic * listener(worker_thread_t *current_thread,
              create thread, but waiting for timer would be an inefficient and
              pointless delay.
            */
-           create_worker(thread_group);
+           create_worker(thread_group, false);
         }
       }
     }
@@ -919,7 +812,7 @@ static void add_thread_count(thread_group_t *thread_group, int32 count)
   per group to prevent deadlocks (one listener + one worker)
 */
 
-static int create_worker(thread_group_t *thread_group)
+static int create_worker(thread_group_t *thread_group, bool due_to_stall)
 {
   pthread_t thread_id;
   bool max_threads_reached= false;
@@ -942,6 +835,11 @@ static int create_worker(thread_group_t *thread_group)
     thread_group->last_thread_creation_time=microsecond_interval_timer();
     statistic_increment(thread_created,&LOCK_status);
     add_thread_count(thread_group, 1);
+    TP_INCREMENT_GROUP_COUNTER(thread_group,thread_creations);
+    if(due_to_stall)
+    {
+      TP_INCREMENT_GROUP_COUNTER(thread_group, thread_creations_due_to_stall);
+    }
   }
   else
   {
@@ -993,15 +891,17 @@ static ulonglong microsecond_throttling_interval(thread_group_t *thread_group)
   Worker creation is throttled, so we avoid too many threads
   to be created during the short time.
 */
-static int wake_or_create_thread(thread_group_t *thread_group)
+static int wake_or_create_thread(thread_group_t *thread_group, bool due_to_stall)
 {
   DBUG_ENTER("wake_or_create_thread");
   
   if (thread_group->shutdown)
    DBUG_RETURN(0);
 
-  if (wake_thread(thread_group) == 0)
+  if (wake_thread(thread_group, due_to_stall) == 0)
+  {
     DBUG_RETURN(0);
+  }
 
   if (thread_group->thread_count > thread_group->connection_count)
     DBUG_RETURN(-1);
@@ -1015,7 +915,7 @@ static int wake_or_create_thread(thread_group_t *thread_group)
      idle  thread to wakeup. Smells like a potential deadlock or very slowly 
      executing requests, e.g sleeps or user locks.
     */
-    DBUG_RETURN(create_worker(thread_group));
+    DBUG_RETURN(create_worker(thread_group, due_to_stall));
   }
 
   ulonglong now = microsecond_interval_timer();
@@ -1026,9 +926,10 @@ static int wake_or_create_thread(thread_group_t *thread_group)
   if (time_since_last_thread_created >
        microsecond_throttling_interval(thread_group))
   {
-    DBUG_RETURN(create_worker(thread_group));
+    DBUG_RETURN(create_worker(thread_group, due_to_stall));
   }
-  
+
+  TP_INCREMENT_GROUP_COUNTER(thread_group,throttles);
   DBUG_RETURN(-1);
 }
 
@@ -1074,7 +975,7 @@ void thread_group_destroy(thread_group_t *thread_group)
   Wake sleeping thread from waiting list
 */
 
-static int wake_thread(thread_group_t *thread_group)
+static int wake_thread(thread_group_t *thread_group,bool due_to_stall)
 {
   DBUG_ENTER("wake_thread");
   worker_thread_t *thread = thread_group->waiting_threads.front();
@@ -1083,6 +984,11 @@ static int wake_thread(thread_group_t *thread_group)
     thread->woken= true;
     thread_group->waiting_threads.remove(thread);
     mysql_cond_signal(&thread->cond);
+    TP_INCREMENT_GROUP_COUNTER(thread_group, wakes);
+    if (due_to_stall)
+    {
+      TP_INCREMENT_GROUP_COUNTER(thread_group, wakes_due_to_stall);
+    }
     DBUG_RETURN(0);
   }
   DBUG_RETURN(1); /* no thread in waiter list => missed wakeup */
@@ -1140,7 +1046,7 @@ static void thread_group_close(thread_group_t *thread_group)
   wake_listener(thread_group);
 
   /* Wake all workers. */
-  while(wake_thread(thread_group) == 0) 
+  while(wake_thread(thread_group, false) == 0) 
   { 
   }
   
@@ -1224,7 +1130,10 @@ TP_connection_generic *get_event(worker_thread_t *current_thread,
     {
       connection = queue_get(thread_group);
       if(connection)
+      {
+        TP_INCREMENT_GROUP_COUNTER(thread_group,dequeues_by_worker);
         break;
+      }
     }
 
     /* If there is  currently no listener in the group, become one. */
@@ -1235,7 +1144,10 @@ TP_connection_generic *get_event(worker_thread_t *current_thread,
       mysql_mutex_unlock(&thread_group->mutex);
 
       connection = listener(current_thread, thread_group);
-
+      if (connection)
+      {
+        TP_INCREMENT_GROUP_COUNTER(thread_group, dequeues_by_listener);
+      }
       mysql_mutex_lock(&thread_group->mutex);
       thread_group->active_thread_count++;
       /* There is no listener anymore, it just returned. */
@@ -1251,9 +1163,9 @@ TP_connection_generic *get_event(worker_thread_t *current_thread,
     */
     if (!oversubscribed)
     {
-
       native_event ev[MAX_EVENTS];
       int cnt = io_poll_wait(thread_group->pollfd, ev, MAX_EVENTS, 0);
+      TP_INCREMENT_GROUP_COUNTER(thread_group, polls_by_worker);
       if (cnt > 0)
       {
         queue_put(thread_group, ev, cnt);
@@ -1300,6 +1212,7 @@ TP_connection_generic *get_event(worker_thread_t *current_thread,
   }
 
   thread_group->stalled= false;
+
   mysql_mutex_unlock(&thread_group->mutex);
  
   DBUG_RETURN(connection);
@@ -1515,7 +1428,7 @@ static int change_group(TP_connection_generic *c,
   new_group->connection_count++;
   /* Ensure that there is a listener in the new group. */
   if (!new_group->thread_count)
-    ret= create_worker(new_group);
+    ret= create_worker(new_group, false);
   mysql_mutex_unlock(&new_group->mutex);
   return ret;
 }
@@ -1775,4 +1688,6 @@ static void print_pool_blocked_message(bool max_threads_reached)
   }
 }
 
+
+
 #endif /* HAVE_POOL_OF_THREADS */

sql/threadpool_generic.h

+/* Copyright(C) 2019 MariaDB
+ *
+ * This program is free software; you can redistribute itand /or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 - 1301 USA*/
+
+#if defined (HAVE_POOL_OF_THREADS)
+#include <my_global.h>
+#include <sql_plist.h>
+#include <my_pthread.h>
+#include <threadpool.h>
+#include <mysqld.h>
+#include <violite.h>
+
+#ifdef _WIN32
+#include <windows.h>
+/* AIX may define this, too ?*/
+#define HAVE_IOCP 
+#endif
+
+
+#ifdef _WIN32
+typedef HANDLE TP_file_handle;
+#else
+typedef int TP_file_handle;
+#define  INVALID_HANDLE_VALUE -1
+#endif
+
+#ifdef __linux__
+#include <sys/epoll.h>
+typedef struct epoll_event native_event;
+#elif defined(HAVE_KQUEUE)
+#include <sys/event.h>
+typedef struct kevent native_event;
+#elif defined (__sun)
+#include <port.h>
+typedef port_event_t native_event;
+#elif defined (HAVE_IOCP)
+typedef OVERLAPPED_ENTRY native_event;
+#else
+#error threadpool is not available on this platform
+#endif
+
+struct thread_group_t;
+
+/* Per-thread structure for workers */
+struct worker_thread_t
+{
+  ulonglong  event_count; /* number of request handled by this thread */
+  thread_group_t* thread_group;
+  worker_thread_t* next_in_list;
+  worker_thread_t** prev_in_list;
+  mysql_cond_t  cond;
+  bool          woken;
+};
+
+typedef I_P_List<worker_thread_t, I_P_List_adapter<worker_thread_t,
+  & worker_thread_t::next_in_list,
+  & worker_thread_t::prev_in_list>,
+  I_P_List_counter
+>
+worker_list_t;
+
+struct TP_connection_generic :public TP_connection
+{
+  TP_connection_generic(CONNECT* c);
+  ~TP_connection_generic();
+
+  virtual int init() { return 0; };
+  virtual void set_io_timeout(int sec);
+  virtual int  start_io();
+  virtual void wait_begin(int type);
+  virtual void wait_end();
+
+  thread_group_t* thread_group;
+  TP_connection_generic* next_in_queue;
+  TP_connection_generic** prev_in_queue;
+  ulonglong abs_wait_timeout;
+  ulonglong enqueue_time;
+  TP_file_handle fd;
+  bool bound_to_poll_descriptor;
+  int waiting;
+#ifdef HAVE_IOCP
+  OVERLAPPED overlapped;
+#endif
+#ifdef _WIN32
+  enum_vio_type vio_type;
+#endif
+};
+
+
+typedef I_P_List<TP_connection_generic,
+  I_P_List_adapter<TP_connection_generic,
+  & TP_connection_generic::next_in_queue,
+  & TP_connection_generic::prev_in_queue>,
+  I_P_List_counter,
+  I_P_List_fast_push_back<TP_connection_generic> >
+  connection_queue_t;
+
+const int NQUEUES = 2; /* We have high and low priority queues*/
+
+struct thread_group_counters_t
+{
+  ulonglong thread_creations;
+  ulonglong thread_creations_due_to_stall;
+  ulonglong wakes;
+  ulonglong wakes_due_to_stall;
+  ulonglong throttles;
+  ulonglong stalls;
+  ulonglong dequeues_by_worker;
+  ulonglong dequeues_by_listener;
+  ulonglong polls_by_listener;
+  ulonglong polls_by_worker;
+};
+
+struct MY_ALIGNED(CPU_LEVEL1_DCACHE_LINESIZE) thread_group_t
+{
+  mysql_mutex_t mutex;
+  connection_queue_t queues[NQUEUES];
+  worker_list_t waiting_threads;
+  worker_thread_t* listener;
+  pthread_attr_t* pthread_attr;
+  TP_file_handle  pollfd;
+  int  thread_count;
+  int  active_thread_count;
+  int  connection_count;
+  /* Stats for the deadlock detection timer routine.*/
+  int io_event_count;
+  int queue_event_count;
+  ulonglong last_thread_creation_time;
+  int  shutdown_pipe[2];
+  bool shutdown;
+  bool stalled;
+  thread_group_counters_t counters;
+};
+
+#define TP_INCREMENT_GROUP_COUNTER(group,var) group->counters.var++;
+
+extern thread_group_t* all_groups;
+#endif
+