Date: Thu, 29 Nov 2007 20:20:37 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: Matt Reimer <mattjreimer@gmail.com> Cc: freebsd-stable@freebsd.org, Pete French <petefrench@ticketswitch.com> Subject: Re: Also seeing 2 x quad-core system slower that 2 x dual core Message-ID: <474F1105.5020708@FreeBSD.org> In-Reply-To: <f383264b0711291106x4b431cbaj56967bb4b8762408@mail.gmail.com> References: <E1IxklH-000ElU-3w@dilbert.ticketswitch.com> <474F0BDF.8070605@FreeBSD.org> <f383264b0711291106x4b431cbaj56967bb4b8762408@mail.gmail.com>
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Matt Reimer wrote: > On Nov 29, 2007 10:58 AM, Kris Kennaway <kris@freebsd.org> wrote: >> Pete French wrote: >>> On the dual core processors this takes about 20 seconds. On the quad >>> cores it takes about 3 minutes! This is true for both the 32 and 64 bit >>> versions of FreeBSD :-( >> That almost certainly has nothing to do with how many CPUs your system >> has, since rm -rf is a single process running on a single core. > > I wonder if I'm seeing this too. Running super-smack on a 2 x quad > core 1.6GHz Dell 1950 I get about 40000 qps, whereas on a 2 x dual > core 3.0GHz box I've seen 80000 qps. Please, let's try to stay focused :) rm -rf has nothing to do with super-smack and vice versa. > Is this expected? It is not very surprising. super-smack is not a good SMP benchmark, it does stupid things like 1-byte I/O, so it is not very scalable nor a good model of real-world database activity. Accounting for your CPUs being twice as fast on the dual core, it roughly says that the benchmark is not scaling beyond 4 CPUs, which is in line with my own observations. Kris
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