Hi Bob, What happens here is that you perform a tiny operation in each transaction, so what you are really testing here is how fast your file system can flush, because with such tiny transactions all of the time is going to be spent in transactional overhead (i.e. flushing transaction logs to the disk).
The reason you see such large differences between Mac OS X and Linux is because Mac OS X cheats. Flushing a file (fdatasync) on Mac does pretty much nothing. The only thing Mac OS X guarantees is that it will write the data that you just flushed before it writes the next data block you flush, so called "ordered writes". This means that you could potentially get data-loss on hard failure, but never in a way that makes your data internally inconsistent. So to give a short answer to your questions: 1) The linux number is reasonable, Mac OS X cheats. 2) What you are testing is the write speed of your disk for writing small chunks of data. Cheers, Tobias On Mon, Apr 18, 2011 at 10:57 PM, Bob Hutchison <[email protected]>wrote: > Hi, > > Using Neo4j 1.3 and the Borneo (Clojure) wrapper I'm getting radically > different performance numbers with identical test code. > > The test is a simple-minded: create two nodes and a relation between them. > No properties, no indexes, all nodes and relations are different. > > On OS X, it takes about 50s to perform that operation 50,000 times, < 0.8s > to do it 500 times. It uses roughly 30-40% of one core to do this. > > On linux it takes about 30s to perform that operation 500 times. The CPU > usage is negligible (really negligible... almost none). > > I cannot explain the difference in behaviour. > > I have two questions: > > 1) is either of these a reasonable number? I hoping the OS X numbers are > not too fast. > > 2) any ideas as to what might be the cause of this? > > The Computers are comparable. The OS X is a 2.8 GHz i7, the linux box is a > 3.something GHz Xeon (I don't remember the details). > > Thanks in advance for any help, > Bob > > _______________________________________________ > Neo4j mailing list > [email protected] > https://lists.neo4j.org/mailman/listinfo/user > -- Tobias Ivarsson <[email protected]> Hacker, Neo Technology www.neotechnology.com Cellphone: +46 706 534857 _______________________________________________ Neo4j mailing list [email protected] https://lists.neo4j.org/mailman/listinfo/user
