> I did some tests with zfs, and results where appallingly bad, but that was > with db size > ram. > > I think the model used by PostgreSQL, as most databases, are very disk block > centric. Using zfs makes it hard to get good performance. But this was some > time ago, maybe things have improved.
I have some hardware that I ran with last week wherein I was *not* able to reproduce any performance difference between ZFS and UFS2. On both UFS2 and ZFS I was seeing the same performance when using a a RAID10 / set of mirrors. I talked with the Dragonfly folk who originally performed these tests and they also saw the same thing: no real performance difference between ZFS and UFS. I ran my tests on a host with 16 drive, 10K SAS, 192GB RAM. I also created a kernel profiling image and ran the 20 concurrent user test under kgprof(1), dtrace, and pmcstat and have the results available: http://people.freebsd.org/~seanc/pg9.3-fbsd10-profiling/ There are some investigations that are ongoing as a result of these findings. The dfly methodology was observed when generating these results. Stay tuned. -sc -- Sean Chittenden s...@chittenden.org > > Palle > >> 21 maj 2014 kl. 18:33 skrev Gezeala M. Bacuño II <geze...@gmail.com>: >> >> Gotcha. >> >> I've been testing using pgbench on FreeBSD 9.0 release + ZFS + pg 9.3.. I >> can reach the freebsd 10 stats on the pdf files if the dataset <RAM. It >> gets way lower if the dataset >RAM. Test was done on pools without L2ARC >> and with/without compression. I also remember increasing a vm.pmap sysctl. >> I'm out of the office right now sick so I can't provide the stats but yes, >> with mmap it is pretty bad.. >> >> Keep us in the loop. I'd like to help on getting the performance data they >> need. >>> On May 20, 2014 11:16 PM, "Palle Girgensohn" <gir...@pingpong.net> wrote: >>> >>> I got no response about how to grab performance data. >>> >>> The PostgreSQL team is also making an effort by setting up machines >>> dedicated to performance measuring and tuning. >>> >>> And freebsd guys and PostgreSQL guys are apparently meeting at pgcon this >>> week. >>> >>> We'll see where that leads. >>> >>> In the mean time, if I for some pointers on how to grab performance data, >>> I could do some more tests. >>> >>> Palle >>> >>> 21 maj 2014 kl. 02:13 skrev Gezeala M. Bacuño II <geze...@gmail.com>: >>> >>> >>> Do you guys have any updates on this? >>> >>> -- >>> >>> regards >>> >>> gezeala bacuño II >>> >>> >>> On Tue, Apr 22, 2014 at 11:52 PM, Palle Girgensohn >>> <gir...@pingpong.net>wrote: >>> >>>> >>>> >>>>> 23 apr 2014 kl. 01:04 skrev Adrian Chadd <adr...@freebsd.org>: >>>>> >>>>> Hi, >>>>> >>>>> Are you able to repeat these tests (for both 9.2 and 9.3) whilst >>>>> grabbing some performance data from lock profiling and hwpmc? >>>> >>>> I sure can, but I'd love some pointers as to how this is done. Please? :-) >>>> >>>>> >>>>> The benchmarking is great but it doesn't tell us enough information as >>>>> to "why" things behave poorly compared to Linux and why the mmap drop >>>>> isn't so great. >>>> >>>> >>>> As per the discussion on postresql-hackers, the regression between pg9.2 >>>> and pg9.3, which includes the sysv->mmap shift, *might* also exist, at >>>> least partly, on Linux as well. >>>> >>>> The initial post in *this* thread does however indicate that freebsd >>>> performs poorer than Linux and dragonflybsd, but does not really compare >>>> PostgreSQL versions. >>>> >>>> Just so we're not pursuing the wrong problem here, let's be open minded >>>> about the definition of the problem. :-) >>>> >>>>> >>>>> What about with more clients? 64? 128? 256? >>>> >>>> My test went to 80. I can go higher as well, though other sources say 50 >>>> is a reasonable limit for PostgreSQL. >>>> >>>> Palle >>>> >>>> >>>>> >>>>> >>>>> Thanks! >>>>> >>>>> >>>>> >>>>> -a >>>>> >>>>> >>>>>> On 21 April 2014 14:11, Palle Girgensohn <gir...@pingpong.net> wrote: >>>>>> >>>>>> >>>>>>> Den torsdagen den 20:e mars 2014 kl. 00:33:10 UTC+1 skrev Sean >>>> Chittenden: >>>>>>> >>>>>>>> As far as I know, the test was done on both UFS2 and ZFS and the >>>>>>>> difference was marginal. >>>>>>> >>>>>>> As Adrian pointed out, there is an mmap(2) mutex in the way. Starting >>>> in >>>>>>> PostgreSQL 9.3, shared buffers are allocated out of mmap(2) instead >>>> of shm. >>>>>>> shm is only used to notify the PostgreSQL postmaster that a child >>>> process >>>>>>> exited/crashed (when a pid detaches from a shm segment, there is a >>>> kernel >>>>>>> event, but there is no kernel event when detaching from an mmap(2) >>>> region). >>>>>>> -sc >>>>>>> >>>>>>> http://www.postgresql.org/docs/9.3/static/release-9-3.html#AEN115039 >>>>>>> >>>>>>> >>>>>>>>>> Just want to share these pgbench results done by DragonFlyBSD, and >>>>>>> would >>>>>>>>>> like some input on why these numbers look so bad and what can be >>>> done >>>>>>> to >>>>>>>>>> improve (ie. kernel tunables etc) the performance. >>>> http://lists.dragonflybsd.org/pipermail/users/attachments/20140310/4250b961/attachment-0001.pdf >>>>>>>>> >>>>>>>>> >>>>>>>>> Do you have the ability to test with FreeBSD 8.x and 9.x to see if >>>> this >>>>>>> is >>>>>>>>> regression? >>>>>>>>> >>>>>>>>> Also you don't mention the FS used in each case, so I'm wondering if >>>>>>> you >>>>>>>>> used a ZFS install of FreeBSD which could help to explain things. >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> Sean Chittenden >>>>>>> se...@chittenden.org <javascript:> >>>>>> Hi, >>>>>> >>>>>> There is a fresh thread about this in postgresql-hackers [1]. >>>>>> >>>>>> There are two parallel approaches suggested there, where one is to >>>> have an >>>>>> option to continue using the old SYSV shared memory in PostgreSQL, and >>>> the >>>>>> other is the suggestion that "somebody needs to hold the FreeBSD folks' >>>>>> feet to the fire about when we can expect to see a fix from their >>>> side." >>>>>> >>>>>> Looking at the original post in this thread, it seems to me that >>>> FreeBSD >>>>>> has scalability problems beyond what the SYSV vs mmap change in >>>> PostgreSQL >>>>>> introduces? Check my test of PostgreSQL 9.2 vs 9.3 on FreeBSD 10.0 at >>>> [1]. >>>>>> The difference between PG92 and PG93 is not huge, ~17%. The difference >>>>>> between FreeBSD and the other OS:es in this thread's original post's >>>>>> performance chart seems to be about a lot more? >>>>>> >>>>>> Palle >>>>>> >>>>>> [1] >>>> http://www.postgresql.org/message-id/2ae143d2-87d3-4ad1-ac78-ce2258230...@freebsd.org >>>>>> _______________________________________________ >>>>>> freebsd-performance@freebsd.org mailing list >>>>>> http://lists.freebsd.org/mailman/listinfo/freebsd-performance >>>>>> To unsubscribe, send any mail to " >>>> freebsd-performance-unsubscr...@freebsd.org" >>>> _______________________________________________ >>>> freebsd-performance@freebsd.org mailing list >>>> http://lists.freebsd.org/mailman/listinfo/freebsd-performance >>>> To unsubscribe, send any mail to " >>>> freebsd-performance-unsubscr...@freebsd.org" >> _______________________________________________ >> freebsd-performance@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-performance >> To unsubscribe, send any mail to >> "freebsd-performance-unsubscr...@freebsd.org" > _______________________________________________ > freebsd-performance@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-performance > To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org" _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org"
