app/vmselect/netstorage: reuse timeseriesWork objects in order to reduce memory allocations

app/vmselect/netstorage/netstorage.go

@@ -91,6 +91,34 @@ type timeseriesWork struct {
 	rowsProcessed int
 }
 
+func (tsw *timeseriesWork) reset() {
+	tsw.mustStop = 0
+	tsw.rss = nil
+	tsw.pts = nil
+	tsw.f = nil
+	if n := len(tsw.doneCh); n > 0 {
+		logger.Panicf("BUG: tsw.doneCh must be empty during reset; it contains %d items instead", n)
+	}
+	tsw.rowsProcessed = 0
+}
+
+func getTimeseriesWork() *timeseriesWork {
+	v := tswPool.Get()
+	if v == nil {
+		v = &timeseriesWork{
+			doneCh: make(chan error, 1),
+		}
+	}
+	return v.(*timeseriesWork)
+}
+
+func putTimeseriesWork(tsw *timeseriesWork) {
+	tsw.reset()
+	tswPool.Put(tsw)
+}
+
+var tswPool sync.Pool
+
 func init() {
 	for i := 0; i < gomaxprocs; i++ {
 		go timeseriesWorker(uint(i))
@@ -147,12 +175,10 @@ func (rss *Results) RunParallel(f func(rs *Result, workerID uint) error) error {
 	// Feed workers with work.
 	tsws := make([]*timeseriesWork, len(rss.packedTimeseries))
 	for i := range rss.packedTimeseries {
-		tsw := &timeseriesWork{
+		tsw := getTimeseriesWork()
-			rss:    rss,
+		tsw.rss = rss
-			pts:    &rss.packedTimeseries[i],
+		tsw.pts = &rss.packedTimeseries[i]
-			f:      f,
+		tsw.f = f
-			doneCh: make(chan error, 1),
-		}
 		timeseriesWorkCh <- tsw
 		tsws[i] = tsw
 	}
@@ -163,7 +189,8 @@ func (rss *Results) RunParallel(f func(rs *Result, workerID uint) error) error {
 	var firstErr error
 	rowsProcessedTotal := 0
 	for _, tsw := range tsws {
-		if err := <-tsw.doneCh; err != nil && firstErr == nil {
+		err := <-tsw.doneCh
+		if err != nil && firstErr == nil {
 			// Return just the first error, since other errors
 			// are likely duplicate the first error.
 			firstErr = err
@@ -173,6 +200,7 @@ func (rss *Results) RunParallel(f func(rs *Result, workerID uint) error) error {
 			}
 		}
 		rowsProcessedTotal += tsw.rowsProcessed
+		putTimeseriesWork(tsw)
 	}
 
 	perQueryRowsProcessed.Update(float64(rowsProcessedTotal))