Neo4j Configuration for 4M Nodes 10M relationship - cypher

Question

I am new to Neo4j and have made few graph queries with 4M nodes and 10M relationships. Till now i've completely surprised from the performance of my queries.
SCHEMA
.......
(a:user{data:1})-[:follow]->(:user)-[:next*1..10]-(:activity)
Here user with data:1 is following another 100,000 user. Each of those 100,000 users have 2-8 next nodes(lets say activity of users) attached. Now i want to fetch the activities of users till next level 3 [:next*1..3] . Each activity has property relevance number.
So now i have 100,000 *3 nodes to traverse.
CYPHER
.......
match (u:user{data:1})-[:follow]-(:user)-[:next*1..3]-(a:activity)
return a order by a.relevance desc limit 50
This query is taking 72000 ms almost every time. Since i am new to Neo4j and i am sure that i haven't done tuning of the OS.
I am using following parameters-
Initial Java Heap Size (in MB)
wrapper.java.initmemory=2000
Maximum Java Heap Size (in MB)
wrapper.java.maxmemory=2456
Default values for the low-level graph engine
neostore.nodestore.db.mapped_memory=25M
neostore.relationshipstore.db.mapped_memory=50M
neostore.propertystore.db.mapped_memory=90M
neostore.propertystore.db.strings.mapped_memory=130M
neostore.propertystore.db.arrays.mapped_memory=130M
Please tell me where i am doing wrong. I read all the documentation from neo4j website but the query time didn't improve.
please tell me how can i configure high performing cache? What should i do so that all the graph loads up in memory? When i see my RAM usage , it is always like 1.8 GB out of 4 Gb. I am using enterprise license on windows (Neo4j 2.0). Please help.

Answer 1

You are actually following not 100k * 3 but, 100k * (2-10)^10 meaning 10^15 paths.
More memory in your machine would make a lot of sense, so try to get 8 or more GB.
Then you can increase the heap, e.g. to 6GB:
wrapper.java.initmemory=6000
wrapper.java.maxmemory=6000
neo4j.properties
neostore.nodestore.db.mapped_memory=100M
neostore.relationshipstore.db.mapped_memory=500M
neostore.propertystore.db.mapped_memory=200M
neostore.propertystore.db.strings.mapped_memory=200M
neostore.propertystore.db.arrays.mapped_memory=10M
If you want to pull your data through, you would most probably want to inverse your query.
match (a:activity),(u:user{data:1})
with a,u
order by a.relevance
desc limit 100
match (followed:user)-[:next*1..3]-(a:activity)
where (followed)-[:follow]-(user)
return a
order by a.relevance
desc limit 50