statistics: add mutex for Handle.globalMap and Handle.feedback

statistics/feedback.go

@@ -130,6 +130,25 @@ func (m *QueryFeedbackMap) append(k QueryFeedbackKey, qs []*QueryFeedback) bool
 	return true
 }
 
+// SiftFeedbacks eliminates feedbacks which are overlapped with others. It is a tradeoff between
+// feedback accuracy and its overhead.
+func (m *QueryFeedbackMap) SiftFeedbacks() {
+	sc := &stmtctx.StatementContext{TimeZone: time.UTC}
+	for k, qs := range m.Feedbacks {
+		fbs := make([]Feedback, 0, len(qs)*2)
+		for _, q := range qs {
+			fbs = append(fbs, q.Feedback...)
+		}
+		if len(fbs) == 0 {
+			delete(m.Feedbacks, k)
+			continue
+		}
+		m.Feedbacks[k] = m.Feedbacks[k][:1]
+		m.Feedbacks[k][0].Feedback, _ = NonOverlappedFeedbacks(sc, fbs)
+	}
+	m.Size = len(m.Feedbacks)
+}
+
 // Merge combines 2 collections of feedbacks.
 func (m *QueryFeedbackMap) Merge(r *QueryFeedbackMap) {
 	for k, qs := range r.Feedbacks {

statistics/handle/handle.go

@@ -99,9 +99,15 @@ type Handle struct {
 	// listHead contains all the stats collector required by session.
 	listHead *SessionStatsCollector
 	// globalMap contains all the delta map from collectors when we dump them to KV.
-	globalMap tableDeltaMap
+	globalMap struct {
+		sync.Mutex
+		data tableDeltaMap
+	}
 	// feedback is used to store query feedback info.
-	feedback *statistics.QueryFeedbackMap
+	feedback struct {
+		sync.Mutex
+		data *statistics.QueryFeedbackMap
+	}
 
 	lease atomic2.Duration
 
@@ -159,6 +165,7 @@ func (h *Handle) execRestrictedSQLWithSnapshot(ctx context.Context, sql string,
 
 // Clear the statsCache, only for test.
 func (h *Handle) Clear() {
+	// TODO: Here h.mu seems to protect all the fields of Handle. Is is reasonable?
 	h.mu.Lock()
 	h.statsCache.Lock()
 	h.statsCache.Store(statsCache{tables: make(map[int64]*statistics.Table)})
@@ -167,13 +174,17 @@ func (h *Handle) Clear() {
 	for len(h.ddlEventCh) > 0 {
 		<-h.ddlEventCh
 	}
-	h.feedback = statistics.NewQueryFeedbackMap()
+	h.feedback.Lock()
+	h.feedback.data = statistics.NewQueryFeedbackMap()
+	h.feedback.Unlock()
 	h.mu.ctx.GetSessionVars().InitChunkSize = 1
 	h.mu.ctx.GetSessionVars().MaxChunkSize = 1
 	h.mu.ctx.GetSessionVars().EnableChunkRPC = false
 	h.mu.ctx.GetSessionVars().SetProjectionConcurrency(0)
 	h.listHead = &SessionStatsCollector{mapper: make(tableDeltaMap), rateMap: make(errorRateDeltaMap)}
-	h.globalMap = make(tableDeltaMap)
+	h.globalMap.Lock()
+	h.globalMap.data = make(tableDeltaMap)
+	h.globalMap.Unlock()
 	h.mu.rateMap = make(errorRateDeltaMap)
 	h.mu.Unlock()
 }
@@ -188,8 +199,6 @@ func NewHandle(ctx sessionctx.Context, lease time.Duration, pool sessionPool) (*
 	handle := &Handle{
 		ddlEventCh:       make(chan *util.Event, 100),
 		listHead:         &SessionStatsCollector{mapper: make(tableDeltaMap), rateMap: make(errorRateDeltaMap)},
-		globalMap:        make(tableDeltaMap),
-		feedback:         statistics.NewQueryFeedbackMap(),
 		idxUsageListHead: &SessionIndexUsageCollector{mapper: make(indexUsageMap)},
 		pool:             pool,
 	}
@@ -199,6 +208,8 @@ func NewHandle(ctx sessionctx.Context, lease time.Duration, pool sessionPool) (*
 	handle.mu.ctx = ctx
 	handle.mu.rateMap = make(errorRateDeltaMap)
 	handle.statsCache.Store(statsCache{tables: make(map[int64]*statistics.Table)})
+	handle.globalMap.data = make(tableDeltaMap)
+	handle.feedback.data = statistics.NewQueryFeedbackMap()
 	err := handle.RefreshVars()
 	if err != nil {
 		return nil, err
@@ -218,10 +229,12 @@ func (h *Handle) SetLease(lease time.Duration) {
 
 // GetQueryFeedback gets the query feedback. It is only used in test.
 func (h *Handle) GetQueryFeedback() *statistics.QueryFeedbackMap {
+	h.feedback.Lock()
 	defer func() {
-		h.feedback = statistics.NewQueryFeedbackMap()
+		h.feedback.data = statistics.NewQueryFeedbackMap()
+		h.feedback.Unlock()
 	}()
-	return h.feedback
+	return h.feedback.data
 }
 
 // DurationToTS converts duration to timestamp.

statistics/handle/update.go

@@ -64,6 +64,12 @@ func (m tableDeltaMap) update(id int64, delta int64, count int64, colSize *map[i
 	m[id] = item
 }
 
+func (m tableDeltaMap) merge(deltaMap tableDeltaMap) {
+	for id, item := range deltaMap {
+		m.update(id, item.Delta, item.Count, &item.ColSize)
+	}
+}
+
 type errorRateDelta struct {
 	PkID         int64
 	PkErrorRate  *statistics.ErrorRate
@@ -125,14 +131,12 @@ func (m errorRateDeltaMap) clear(tableID int64, histID int64, isIndex bool) {
 	m[tableID] = item
 }
 
-func (h *Handle) merge(s *SessionStatsCollector, rateMap errorRateDeltaMap) {
-	for id, item := range s.mapper {
-		h.globalMap.update(id, item.Delta, item.Count, &item.ColSize)
-	}
+func merge(s *SessionStatsCollector, deltaMap tableDeltaMap, rateMap errorRateDeltaMap, feedback *statistics.QueryFeedbackMap) {
+	deltaMap.merge(s.mapper)
 	s.mapper = make(tableDeltaMap)
 	rateMap.merge(s.rateMap)
 	s.rateMap = make(errorRateDeltaMap)
-	h.feedback.Merge(s.feedback)
+	feedback.Merge(s.feedback)
 	s.feedback = statistics.NewQueryFeedbackMap()
 }
 
@@ -375,13 +379,15 @@ const (
 // sweepList will loop over the list, merge each session's local stats into handle
 // and remove closed session's collector.
 func (h *Handle) sweepList() {
+	deltaMap := make(tableDeltaMap)
+	errorRateMap := make(errorRateDeltaMap)
+	feedback := statistics.NewQueryFeedbackMap()
 	prev := h.listHead
 	prev.Lock()
-	errorRateMap := make(errorRateDeltaMap)
 	for curr := prev.next; curr != nil; curr = curr.next {
 		curr.Lock()
-		// Merge the session stats into handle and error rate map.
-		h.merge(curr, errorRateMap)
+		// Merge the session stats into deltaMap, errorRateMap and feedback respectively.
+		merge(curr, deltaMap, errorRateMap, feedback)
 		if curr.deleted {
 			prev.next = curr.next
 			// Since the session is already closed, we can safely unlock it here.
@@ -393,37 +399,34 @@ func (h *Handle) sweepList() {
 		}
 	}
 	prev.Unlock()
+	h.globalMap.Lock()
+	h.globalMap.data.merge(deltaMap)
+	h.globalMap.Unlock()
 	h.mu.Lock()
 	h.mu.rateMap.merge(errorRateMap)
 	h.mu.Unlock()
-	h.siftFeedbacks()
-}
-
-// siftFeedbacks eliminates feedbacks which are overlapped with others. It is a tradeoff between
-// feedback accuracy and its overhead.
-func (h *Handle) siftFeedbacks() {
-	sc := &stmtctx.StatementContext{TimeZone: time.UTC}
-	for k, qs := range h.feedback.Feedbacks {
-		fbs := make([]statistics.Feedback, 0, len(qs)*2)
-		for _, q := range qs {
-			fbs = append(fbs, q.Feedback...)
-		}
-		if len(fbs) == 0 {
-			delete(h.feedback.Feedbacks, k)
-			continue
-		}
-		h.feedback.Feedbacks[k] = h.feedback.Feedbacks[k][:1]
-		h.feedback.Feedbacks[k][0].Feedback, _ = statistics.NonOverlappedFeedbacks(sc, fbs)
-	}
-	h.feedback.Size = len(h.feedback.Feedbacks)
+	h.feedback.Lock()
+	h.feedback.data.Merge(feedback)
+	h.feedback.data.SiftFeedbacks()
+	h.feedback.Unlock()
 }
 
 // DumpStatsDeltaToKV sweeps the whole list and updates the global map, then we dumps every table that held in map to KV.
 // If the mode is `DumpDelta`, it will only dump that delta info that `Modify Count / Table Count` greater than a ratio.
 func (h *Handle) DumpStatsDeltaToKV(mode dumpMode) error {
 	h.sweepList()
+	h.globalMap.Lock()
+	deltaMap := h.globalMap.data
+	h.globalMap.data = make(tableDeltaMap)
+	h.globalMap.Unlock()
+	defer func() {
+		h.globalMap.Lock()
+		deltaMap.merge(h.globalMap.data)
+		h.globalMap.data = deltaMap
+		h.globalMap.Unlock()
+	}()
 	currentTime := time.Now()
-	for id, item := range h.globalMap {
+	for id, item := range deltaMap {
 		if mode == DumpDelta && !needDumpStatsDelta(h, id, item, currentTime) {
 			continue
 		}
@@ -432,17 +435,17 @@ func (h *Handle) DumpStatsDeltaToKV(mode dumpMode) error {
 			return errors.Trace(err)
 		}
 		if updated {
-			h.globalMap.update(id, -item.Delta, -item.Count, nil)
+			deltaMap.update(id, -item.Delta, -item.Count, nil)
 		}
 		if err = h.dumpTableStatColSizeToKV(id, item); err != nil {
 			return errors.Trace(err)
 		}
 		if updated {
-			delete(h.globalMap, id)
+			delete(deltaMap, id)
 		} else {
-			m := h.globalMap[id]
+			m := deltaMap[id]
 			m.ColSize = nil
-			h.globalMap[id] = m
+			deltaMap[id] = m
 		}
 	}
 	return nil
@@ -522,8 +525,12 @@ func (h *Handle) dumpTableStatColSizeToKV(id int64, delta variable.TableDelta) e
 
 // DumpStatsFeedbackToKV dumps the stats feedback to KV.
 func (h *Handle) DumpStatsFeedbackToKV() error {
+	h.feedback.Lock()
+	feedback := h.feedback.data
+	h.feedback.data = statistics.NewQueryFeedbackMap()
+	h.feedback.Unlock()
 	var err error
-	for _, fbs := range h.feedback.Feedbacks {
+	for _, fbs := range feedback.Feedbacks {
 		for _, fb := range fbs {
 			if fb.Tp == statistics.PkType {
 				err = h.DumpFeedbackToKV(fb)
@@ -548,7 +555,6 @@ func (h *Handle) DumpStatsFeedbackToKV() error {
 			}
 		}
 	}
-	h.feedback = statistics.NewQueryFeedbackMap()
 	return errors.Trace(err)
 }
 
@@ -581,8 +587,12 @@ func (h *Handle) DumpFeedbackToKV(fb *statistics.QueryFeedback) error {
 // feedback locally on this tidb-server, so it could be used more timely.
 func (h *Handle) UpdateStatsByLocalFeedback(is infoschema.InfoSchema) {
 	h.sweepList()
+	h.feedback.Lock()
+	feedback := h.feedback.data
+	h.feedback.data = statistics.NewQueryFeedbackMap()
+	h.feedback.Unlock()
 OUTER:
-	for _, fbs := range h.feedback.Feedbacks {
+	for _, fbs := range feedback.Feedbacks {
 		for _, fb := range fbs {
 			h.mu.Lock()
 			table, ok := h.getTableByPhysicalID(is, fb.PhysicalID)

statistics/handle/update_list_test.go

@@ -25,8 +25,8 @@ func TestInsertAndDelete(t *testing.T) {
 	t.Parallel()
 	h := Handle{
 		listHead: &SessionStatsCollector{mapper: make(tableDeltaMap)},
-		feedback: statistics.NewQueryFeedbackMap(),
 	}
+	h.feedback.data = statistics.NewQueryFeedbackMap()
 	var items []*SessionStatsCollector
 	for i := 0; i < 5; i++ {
 		items = append(items, h.NewSessionStatsCollector())