Rick, I don't quite understand what you are asking for. Could you elaborate further?
-tobias 2011/3/22 Rick Bullotta <rick.bullo...@thingworx.com> > I'd like to explore this question a bit further. Does this mean that > basically there's no way to scale beyond a single thread/CPU for > disconnected graphs if you have complex graph dependencies (e.g. you cannot > create disjoint subgraphs)? > > > > -----Original Message----- > From: user-boun...@lists.neo4j.org [mailto:user-boun...@lists.neo4j.org] > On Behalf Of Tobias Ivarsson > Sent: Saturday, March 19, 2011 5:59 AM > To: Neo4j user discussions > Subject: Re: [Neo4j] Fans of Neo4j From Chinese > > Neo4j serializes commits. I.e. at most one thread is committing a > transaction at once. > For the actual work of building up the data to be committed, Neo4j supports > multiple concurrent threads. > > This fact alone, that there is a single congestion point, means that if an > application, like in your case, is very write centric, it is unlikely for > it > to scale beyond two threads, with one building up the next commit while the > other is commiting its data. It might scale to a few more threads than that > if the buildup time is significantly larger than the commit time. It is > simple time slicing, "only one train can be at the station at once", then > you have to do the maths on how many "trains can be out on the track" > during > that time. > > It is also worth keeping in mind, that for CPU bound operation, an > application doesn't scale much further than the number of CPUs in the > computer. The threads that are not in commit mode - i.e. the ones that are > building up the data for their next commit - are CPU bound, and contending > for the same CPU resources. This means that your application is not going > to > scale much further than the number of CPUs in your computer, and few > desktop/laptop computers have more than 4 CPUs these days, which makes 5 > threads about the most you can squeeze out of it, anything more than that > is > just going to add contention, and possibly even slow things down. > > Finally, the (CPU bound) threads that create the graph might be contending > on the same resources. As Peter said. If multiple threads modify the same > node or relationship, i.e. if they create relationships to the same node > (the root node for example), they are all going to block on that resource. > Neo4j only allows one transaction to modify each entity at a time. This > means that to get maximum concurrency out of your data creation, each > thread > should be creating each own disconnected subgraph. And if they have > connected parts, the connections to the "global data" should be made last > in > the transaction (in a predictable order to avoid deadlocks[1]), to maximize > the time the thread is operational before hitting the > "congestion point" that is the (potentially) contended data. > > Cheers, > Tobias > > [1] Neo4j will detect if a deadlock has occurred and throw a > DeadlockDetectedException in that case. > > 2011/3/18 孤竹 <ho...@foxmail.com> > > > hi, > > > > > > Sorry for disturb you , I am a chinese engineer , Excused for my bad > > english :) . > > > > > > Recently, I am learning Neo4j and trying to use it in my project . But > > When I make a Pressure on neo4j with 5 theads , 10 theads, 20 and 30, I > > found the nodes inserted to the Neo4J is not change obvious (sometimes > not > > change ~ ~! ). Does it not matter with threads ? the kenerl will make it > > Serial ? Is there any documents or something about The performance of > Neo4j > > ? thanks for your help > > > > > > > > The program as follows: > > I put this function in ExecutorService ,with 5/10/30 threads. then test > > for the nodes inserted into at same time .(The counts have not changed > > obviously) > > > > > > Transaction tx = null; > > Node before = null; > > try { > > for (int i = 0; i < 1000000; i++) { > > if(stop == true){ > > return; > > } > > if (graphDb == null) { > > return; > > } > > try { > > if (tx == null) { > > tx = graphDb.beginTx(); > > } > > // 引用计数加1 > > writeCount.addAndGet(1); > > int startNodeString = > > name.addAndGet(1); > > Node start = > > getOrCreateNodeWithOutIndex("" > > + > startNodeString); > > if (before == null) { > > // 根节点.哈哈哈 I got U > > Node root = > > graphDb.getNodeById(0); > > > > root.createRelationshipTo(start, LEAD); > > } > > if (before != null) { > > > > before.createRelationshipTo(start, LOVES); > > } > > int endNodeName = > name.addAndGet(1); > > Node end = > > getOrCreateNodeWithOutIndex("" + endNodeName); > > start.createRelationshipTo(end, > > KNOWS); > > before = end; > > // 每一千次 commit一次 > > if (i % 100 == 0) { > > tx.success(); > > tx.finish(); > > tx = null; > > } > > } catch (Exception e) { > > System.out.println("write : = " + > > e); > > } > > } > > } catch (Exception e) { > > } finally { > > tx.finish(); > > } > > } > > > -- > Tobias Ivarsson <tobias.ivars...@neotechnology.com> > Hacker, Neo Technology > www.neotechnology.com > Cellphone: +46 706 534857 > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > _______________________________________________ > Neo4j mailing list > User@lists.neo4j.org > https://lists.neo4j.org/mailman/listinfo/user > -- Tobias Ivarsson <tobias.ivars...@neotechnology.com> Hacker, Neo Technology www.neotechnology.com Cellphone: +46 706 534857 _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
