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
(cherry picked from commit d3f7c0196ecf58b78574d8b80e1844ecb4e223d6)

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 1e4b5cbac508623fff9fd9d5017043818ce1ee42..52be328eb87ea5de7d9b58fed20e1fe53439f727 100644 (file)
--- 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()) {