[IMPROVED] Publish performance with lots of no interest subjects (#4359)

Do not hold onto no interest subjects from a client in the unlocked cache.
If sending lots of different subjects all with no interest performance could be affected.

Signed-off-by: Derek Collison <derek@nats.io>

Resolves #4341

server/client.go

@@ -3670,14 +3670,16 @@ func (c *client) processInboundClientMsg(msg []byte) (bool, bool) {
 	// Go back to the sublist data structure.
 	if !ok {
 		r = acc.sl.Match(string(c.pa.subject))
-		c.in.results[string(c.pa.subject)] = r
-		// Prune the results cache. Keeps us from unbounded growth. Random delete.
-		if len(c.in.results) > maxResultCacheSize {
-			n := 0
-			for subject := range c.in.results {
-				delete(c.in.results, subject)
-				if n++; n > pruneSize {
-					break
+		if len(r.psubs)+len(r.qsubs) > 0 {
+			c.in.results[string(c.pa.subject)] = r
+			// Prune the results cache. Keeps us from unbounded growth. Random delete.
+			if len(c.in.results) > maxResultCacheSize {
+				n := 0
+				for subject := range c.in.results {
+					delete(c.in.results, subject)
+					if n++; n > pruneSize {
+						break
+					}
 				}
 			}
 		}

server/sublist.go

@@ -48,7 +48,7 @@ const (
 	// cacheMax is used to bound limit the frontend cache
 	slCacheMax = 1024
 	// If we run a sweeper we will drain to this count.
-	slCacheSweep = 512
+	slCacheSweep = 256
 	// plistMin is our lower bounds to create a fast plist for Match.
 	plistMin = 256
 )