neo4j update properties on 10 million nodes

I use the neo4j java core api and want to update 10 million nodes. I thought it will be better to do it with multithreading but the performance is not that good (35 minutes for setting properties).

To explain: Each node "Person" has at least one relation "POINTSREL" to a "Point" node, which has the property "Points". I want to sum up the points from the "Point" node and set it as property to the "Person" node.

Here is my code:

Transaction transaction = service.beginTx();
ResourceIterator<Node> iterator = service.findNodes(Labels.person);
transaction.success();
transaction.close();

ExecutorService executor = Executors.newFixedThreadPool(5);

while(iterator.hasNext()){
    executor.execute(new MyJob(iterator.next()));
}

//wait until all threads are done
executor.shutdown();

try {
    executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
} catch (InterruptedException e) {
    e.printStackTrace();
}

And here the runnable class

private class MyJob implements Runnable {

    private Node node;

    /* collect useful parameters in the constructor */
    public MyJob(Node node) {
        this.node = node;
    }

    public void run() {
        Transaction transaction = service.beginTx();
        Iterable<org.neo4j.graphdb.Relationship> rel = this.node.getRelationships(RelationType.POINTSREL, Direction.OUTGOING);

        double sum = 0;
        for(org.neo4j.graphdb.Relationship entry : rel){
            try{
                sum += (Double)entry.getEndNode().getProperty("Points");
            } catch(Exception e){
                e.printStackTrace();
            }
        }
        this.node.setProperty("Sum", sum);

        transaction.success();
        transaction.close();
    }
}

Is there a better (faster) way to do that?

About my setting: AWS Instance with 8 CPUs and 32GB ram

neo4j-wrapper.conf

# Java Heap Size: by default the Java heap size is dynamically
# calculated based on available system resources.
# Uncomment these lines to set specific initial and maximum
# heap size in MB.
wrapper.java.initmemory=16000
wrapper.java.maxmemory=16000

neo4j.properties

# The type of cache to use for nodes and relationships.
cache_type=soft
cache.memory_ratio=30.0
neostore.nodestore.db.mapped_memory=2G
neostore.relationshipstore.db.mapped_memory=7G
neostore.propertystore.db.mapped_memory=2G
neostore.propertystore.db.strings.mapped_memory=2G
neostore.propertystore.db.arrays.mapped_memory=512M

I found out that there was, amongst others, a problem with the property "cache_type=soft". I set it to "cache_type=none" and the duration of the execution decreased from 30 minutes to 2 minutes. After some updates there were always threads which were blocked for about 30 seconds - changing this property helps to avoid these blockings. I will search for a more detail explantation.