Date: Sat, 28 Jun 2014 13:37:20 +0200 From: Palle Girgensohn <girgen@pingpong.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>, "performance@freebsd.org" <performance@freebsd.org>, John Baldwin <jhb@freebsd.org> Subject: Re: PostgreSQL performance on FreeBSD Message-ID: <B97CF825-B9C3-4D46-A26C-7EF56CD5D216@pingpong.net> In-Reply-To: <20140628102137.GA93733@kib.kiev.ua> References: <20140627125613.GT93733@kib.kiev.ua> <201406271057.53599.jhb@freebsd.org> <20140627163407.GX93733@kib.kiev.ua> <35090A62-2DB8-493C-A5ED-ADB1BC193640@pingpong.net> <20140628102137.GA93733@kib.kiev.ua>
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> 28 jun 2014 kl. 12:21 skrev Konstantin Belousov <kostikbel@gmail.com>: >=20 >> On Sat, Jun 28, 2014 at 12:08:39PM +0200, Palle Girgensohn wrote: >>=20 >>=20 >>> 27 jun 2014 kl. 18:34 skrev Konstantin Belousov <kostikbel@gmail.com>: >>>=20 >>>> On Fri, Jun 27, 2014 at 10:57:53AM -0400, John Baldwin wrote: >>>>> On Friday, June 27, 2014 8:56:13 am Konstantin Belousov wrote: >>>>> Hi, >>>>> I did some measurements and hacks to see about the performance and >>>>> scalability of PostgreSQL 9.3 on FreeBSD, sponsored by The FreeBSD >>>>> Foundation. >>>>>=20 >>>>> The results are described in https://kib.kiev.ua/kib/pgsql_perf.pdf. >>>>> The uncommitted patches, referenced in the article, are available as >>>>> https://kib.kiev.ua/kib/pig1.patch.txt >>>>> https://kib.kiev.ua/kib/patch-2 >>>>=20 >>>> Did you run the same benchmark on the same hardware with any other OS's= to=20 >>>> compare results? >>>=20 >>> No. >>>=20 >>> FWIW, before the failing after the 30 clients is corrected, I do not >>> think it is much interesting to do such comparision. >>=20 >> This is great work! >>=20 >> Does anybody know how far back in FreeBSD versions using posix semaphore i= nstead of sysv would make a difference? It seems we need a rather current v= ersion? 8.x did not support it at all, at some point at lest, and in 9 it wa= s buggy. I could add he patch-2 to the port, but I reckon it needs a conditi= onal based on FreeBSD version? > I recommend to add it as an option. The currently supported versions > of stable/9 and higher have new posix semaphores implementation. > The stable/8 also has posix semaphores, but there it is kernel-based > interface, I do not plan to evaluate it in any way. According to one source, posix semaphores uses O(N^2) file descriptors, wher= e N is the number of connections. Do you know if this is true? (I'll try it,= naturally, just checking).=20 >=20 >=20 >> The clang bug should go upstreams, right? > I believe there is already some activity about it. I do not follow > clang development. Sounds good enough.=20 >=20 >>=20 >> I have seen similar curves, presented by Greg Smith (PostgreSQL >> hacker) where he concluded that there is no point in running more >> than 50 concurrent connections. This was for Linux. In your measures, >> the knee is at 30. That's said, FreeBSD could and should do better, >> but probably there is a limit where there will be a knee in the graph >> and performance will drop. It should be more than 30, though, as you >> rightly commented. >>=20 >> Do you any ideas to pursue this further apart from complicated >> rewrites like DragonFly? > I do. >=20 > The scope of the current work was done to obtain understanding where do we= stay > and, if possible, evaluate ideas, possibly in the hackish way. I hope > and almost sure that this will be continued, but cannot provide any time > estimation. Great. If you need help testing, I might be able to help.=20 Cheers, Palle=
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