Hi Tobias, On 2011-04-19, at 1:48 AM, Tobias Ivarsson wrote:
> 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. Okay, that's makes some sense. Thanks for the information. > > 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. So you're thinking that 16 or 17 writes is what should be expected? Cheers, Bob > > Cheers, > Tobias > > On Mon, Apr 18, 2011 at 10:57 PM, Bob Hutchison > <hutch-li...@recursive.ca>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 >> 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 ---- Bob Hutchison Recursive Design Inc. http://www.recursive.ca/ weblog: http://xampl.com/so _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
