Hey mate, yeah, this does clarify it. It is very likely that what is happening is that the OS is caching the index files in RAM, so the second time you run the database (even after a restart), it does not have to hit disk. You could verify that this is the case by evicting the OS page cache between your benchmarks. What OS are you using?
On linux, see: http://linux-mm.org/Drop_Caches On mac, you should be able to run 'purge' to clear the caches, see: http://www.cnet.com/news/purge-the-os-x-disk-cache-to-analyze-memory-usage/ For windows there does not seem to be a vendor-provided mechanism to do this, see here for alternatives: http://stackoverflow.com/questions/7405868/how-to-invalidate-the-file-system-cache /jake On Wed, Nov 19, 2014 at 12:25 PM, 'Curtis Mosters' via Neo4j < [email protected]> wrote: > Hi Jacob, well yeah here is an example: > > START n=node:titles("title:solar") RETURN count(*) > > If I do this right after the import. It needs *180 sec*. But doing this a > second time needs *3 sec* and after that again just needs 1,5 sec, but > after that there is no more improvement. Also after doing some stuff in the > settings, I never get to the 180 sec again.=/ > > But if you think now it is just that word. No it's not. Also tested 9 > others and here it was lasting round about 60 sec, too. But searching again > on them was 1-2 sec. > > Also after restarting the Neo4j server it is still that fast (1-3 sec). > And yeah I need the uncached result time for my comparison. It is not > correct if I continue now with cached things. > > Maybe now it's way clearer? If not just let me know. Thank you. > > Am Mittwoch, 19. November 2014 18:35:38 UTC+1 schrieb Jacob Hansson: >> >> Curtis, >> >> can you clarify what you mean by caching, and how you are determining >> that things are getting cached? >> >> If you are talking about caching of the actual data, note that there are >> several layers of caching - the OS will cache files in its page cache, for >> instance. If you want to work around that in your testing you need to ask >> the operating system to flush its caches. >> >> /j >> >> On Wed, Nov 19, 2014 at 7:36 AM, 'Curtis Mosters' via Neo4j < >> [email protected]> wrote: >> >>> Well for my Benchmark I need a clear Cache because otherwhise Neo4j is >>> always caching and faking my results in a bad way. >>> >>> So I tried: >>> cache_type=none >>> cache.memory_ratio=0.0 >>> >>> >>> >>> in the neo4j.properties. Had no real impact still caching. >>> >>> Also found something from Michael with jconsole: >>> http://stackoverflow.com/questions/26189351/neo4j- >>> server-clear-the-cache-in-ram >>> But really no idea what he means. =( I meant the JMX call I found >>> http://stackoverflow.com/questions/12621963/clear- >>> ehcache-of-remote-server >>> But also not sure if it is the right thing to clear. >>> >>> Here I found infos about the caching: http://neo4j.com/docs/stable/ >>> configuration-caches.html >>> But nothing worked or was in my mind useful to test. >>> >>> Then I gone through all settings here: http://neo4j.com/docs/stable/ >>> kernel-configuration.html >>> But yeah except the two lines above nothing looking satisfying. Even >>> tried query_cache_size=0 but here I got a funny error message then, so yeah >>> dunno what that setting means. >>> >>> Then I was thinking that setting the neo_mapping stuff to 0 might help. >>> But then I found http://grokbase.com/t/gg/neo4j/1312y592r4/caching-the- >>> whole-graph which says that setting to 0 is like limiting to infinity. >>> >>> Ohman so nothing worked to disable the cache. Why is it so hard to give >>> a setting disable cache or clearing the cache after server is shut down. >>> >>> Really need this =/ >>> >>> Thank you >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Neo4j" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> >> -- > You received this message because you are subscribed to the Google Groups > "Neo4j" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Neo4j" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
