From: Tuukka Lehtonen <tuukka.lehtonen@semantum.fi>
Date: Thu, 4 Jun 2020 22:33:16 +0000 (+0300)
Subject: Avoid useless reallocation of empty TreeMaps and map iterators
X-Git-Url: https://gerrit.simantics.org/r/gitweb?p=simantics%2Fplatform.git;a=commitdiff_plain;h=refs%2Fchanges%2F94%2F4294%2F1

Avoid useless reallocation of empty TreeMaps and map iterators

The problem was that when the database is doing work, MainProgram.run
runs in pretty much busy loop mode and previously it was always
allocating a new TreeMap on each round and also calling Map.entrySet()
to get construct iterators for empty TreeMaps which eventually
accumulates up to somewhat signinificant amount of memory allocated.

Possibly an even more efficient way would be to have the Map be a closed
hashing hashmap instead and then sorting the data for iteration
separately.

gitlab #548

Change-Id: Ib2208dc35b270c9d682362d45f24f1fe01bb8969
---

diff --git a/bundles/org.simantics.acorn/src/org/simantics/acorn/MainProgram.java b/bundles/org.simantics.acorn/src/org/simantics/acorn/MainProgram.java
index 1e4b5cbac..52be328eb 100644
--- a/bundles/org.simantics.acorn/src/org/simantics/acorn/MainProgram.java
+++ b/bundles/org.simantics.acorn/src/org/simantics/acorn/MainProgram.java
@@ -70,7 +70,7 @@ public class MainProgram implements Runnable, Closeable {
 		this.updateSchedules = new ArrayList[CLUSTER_THREADS];
 		for(int i=0;i<clusterUpdateThreads.length;i++) {
 			clusterUpdateThreads[i] = Executors.newSingleThreadExecutor(new ClusterThreadFactory("Cluster Updater " + (i+1), false));
-			updateSchedules[i] = new ArrayList<ClusterUpdateOperation>();
+			updateSchedules[i] = new ArrayList<>();
 		}
 	}
 
@@ -93,11 +93,13 @@ public class MainProgram implements Runnable, Closeable {
 
 		try {
 
+			TreeMap<ClusterUID, List<ClusterUpdateOperation>> updates = new TreeMap<>(clusterComparator);
+
 			main:
 			while(alive) {
 
-				TreeMap<ClusterUID, List<ClusterUpdateOperation>> updates = new TreeMap<ClusterUID, List<ClusterUpdateOperation>>(clusterComparator);
-
+				if (!updates.isEmpty())
+					updates.clear();
 				operationQueue.pumpUpdates(updates);
 
 				if(updates.isEmpty()) {
@@ -165,6 +167,9 @@ public class MainProgram implements Runnable, Closeable {
 		for(int i=0;i<CLUSTER_THREADS;i++)
 			updateSchedules[i].clear();
 
+		if (updates.isEmpty())
+			return;
+
 		final Semaphore s = new Semaphore(0);
 
 		for(Map.Entry<ClusterUID, List<ClusterUpdateOperation>> entry : updates.entrySet()) {