Date: Wed, 23 Apr 2014 08:52:57 +0200 From: Palle Girgensohn <girgen@pingpong.net> To: Adrian Chadd <adrian@freebsd.org> Cc: "bsdmailinglist@googlegroups.com" <bsdmailinglist@googlegroups.com>, FreeBSD Mailing Lists <freebsd-performance@freebsd.org>, Sean Chittenden <sean@chittenden.org>, Petr Janda <janda.petr@gmail.com>, Steven Hartland <killing@multiplay.co.uk> Subject: Re: FreeBSD 10 and PostgreSQL 9.3 scalability issues Message-ID: <572540F9-13E4-4BA9-88AE-5F47FB19450A@pingpong.net> In-Reply-To: <CAJ-VmomVOWFb7X5s-amRX7QFzbmT6Kt6bB9gaPVv2_hGx1OS5g@mail.gmail.com> References: <5327B9B7.3050103@gmail.com> <2610F490C952470C9D15999550F67068@multiplay.co.uk> <532A192A.1070509@gmail.com> <assp.0155c70d29.23ED6415-945D-4DF5-90DD-2F2CD7E198AF@chittenden.org> <f4ead73a-fae2-4eac-8499-3cf630eb3d31@googlegroups.com> <CAJ-VmomVOWFb7X5s-amRX7QFzbmT6Kt6bB9gaPVv2_hGx1OS5g@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> 23 apr 2014 kl. 01:04 skrev Adrian Chadd <adrian@freebsd.org>: >=20 > Hi, >=20 > 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? :-) >=20 > 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 pa= rtly, on Linux as well. The initial post in *this* thread does however indicate that freebsd perform= s 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 abou= t the definition of the problem. :-) >=20 > 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.=20 Palle=20 >=20 >=20 > Thanks! >=20 >=20 >=20 > -a >=20 >=20 >> On 21 April 2014 14:11, Palle Girgensohn <girgen@pingpong.net> wrote: >>=20 >>=20 >>> Den torsdagen den 20:e mars 2014 kl. 00:33:10 UTC+1 skrev Sean Chittende= n: >>>=20 >>>> As far as I know, the test was done on both UFS2 and ZFS and the >>>> difference was marginal. >>>=20 >>> 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 s= hm. >>> shm is only used to notify the PostgreSQL postmaster that a child proces= s >>> exited/crashed (when a pid detaches from a shm segment, there is a kerne= l >>> event, but there is no kernel event when detaching from an mmap(2) regio= n). >>> -sc >>>=20 >>> http://www.postgresql.org/docs/9.3/static/release-9-3.html#AEN115039 >>>=20 >>>=20 >>>>>> 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/20140310/4250b= 961/attachment-0001.pdf >>>>>=20 >>>>>=20 >>>>> Do you have the ability to test with FreeBSD 8.x and 9.x to see if thi= s >>> is >>>>> regression? >>>>>=20 >>>>> 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. >>>=20 >>>=20 >>> -- >>> Sean Chittenden >>> se...@chittenden.org <javascript:> >> Hi, >>=20 >> There is a fresh thread about this in postgresql-hackers [1]. >>=20 >> There are two parallel approaches suggested there, where one is to have a= n >> option to continue using the old SYSV shared memory in PostgreSQL, and th= e >> 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." >>=20 >> 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 PostgreSQ= L >> 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? >>=20 >> Palle >>=20 >> [1] >> http://www.postgresql.org/message-id/2AE143D2-87D3-4AD1-AC78-CE2258230C05= @FreeBSD.org >> _______________________________________________ >> freebsd-performance@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-performance >> To unsubscribe, send any mail to "freebsd-performance-unsubscribe@freebsd= .org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?572540F9-13E4-4BA9-88AE-5F47FB19450A>