Date: Fri, 16 Dec 2011 14:08:01 +0100 From: Stefan Esser <se@freebsd.org> To: "O. Hartmann" <ohartman@zedat.fu-berlin.de> Cc: Joe Holden <lists@rewt.org.uk>, FreeBSD Stable Mailing List <freebsd-stable@freebsd.org>, Current FreeBSD <freebsd-current@freebsd.org>, Arnaud Lacombe <lacombar@gmail.com>, freebsd-performance@freebsd.org, Jeremy Chadwick <freebsd@jdc.parodius.com> Subject: Re: Benchmark (Phoronix): FreeBSD 9.0-RC2 vs. Oracle Linux 6.1 Server Message-ID: <4EEB42B1.1000506@freebsd.org> In-Reply-To: <4EEAEDE1.50604@zedat.fu-berlin.de> References: <4EE1EAFE.3070408@m5p.com> <CAJ-FndDniGH8QoT=kUxOQ%2BzdVhWF0Z0NKLU0PGS-Gt=BK6noWw@mail.gmail.com> <4EE2AE64.9060802@m5p.com> <4EE88343.2050302@m5p.com> <CAFHbX1%2B5PttyZuNnYot8emTn_AWkABdJCvnpo5rcRxVXj0ypJA@mail.gmail.com> <4EE933C6.4020209@zedat.fu-berlin.de> <CAPjTQNEJDE17TLH-mDrG_-_Qa9R5N3mSeXSYYWtqz_DFidzYQw@mail.gmail.com> <20111215024249.GA13557@icarus.home.lan> <4EE9A2A0.80607@zedat.fu-berlin.de> <CACqU3MWiMpUNJ9d2t=OxfDHD47evvkgKcwLkiNBgEheWFJrzjw@mail.gmail.com> <4EEAE8DF.40303@rewt.org.uk> <4EEAEDE1.50604@zedat.fu-berlin.de>
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Am 16.12.2011 08:06, schrieb O. Hartmann: > For the underlying OS, as far as I know, the compiler hasn't as much > impact as on userland software since autovectorization and other neat > things are not used during system build. > > From my experience using gcc 4.2 or 4.4/4.5 does not have an impact > beyond 3% when SSE isn't explicetly enforced. Well, but the compute intensive tests showed performance variance of a few percents only, IIRC. The big differences were in the parts that heavily depend on file system and buffer cache concepts (i.e. the low limit on dirty buffers in FreeBSD, which is very beneficial in real world situations; do you remember the first few releases of SunOS-4, which heavily suffered in interactive performance due to a naive unified buffer cache VM system that did not limit the amount of dirty buffers? It caused interactive shells to be swapped out within seconds on systems with background jobs writing to disk). > More interesting is the performance gain due to the architecture. I > think it would be very easy for M. Larabel to repeat this benchmark with > a "bleeding edge" Ubuntu or Suse as well. And since FreeBSD 9.0 can be > compiled with CLANG, it should be possible to compare both also with > "bleeding edge" compilers, say FreeBSD 9/CLANG, Ubuntu 12/gcc 4.6.2. Clang may be considered "bleeding edge", but in quite a different way than gcc-4.6.2. While the latter can look back on 2 decades of development, clang is still in a state where feature completeness (and bug-to-bug compatibility with GCC ;-) is much more important than performance. there is much promise of powerful optimizations becoming available in clang once it is mature, but just now expect GCC 4.6.2 to deliver 5% to 10% higher performance than clang. But as stated before: To exclude compiler dependencies just run the Linux binaries on FreeBSD. There is slight emulation overhead and Glibc is not particularly optimized for FreeBSD, but this will still provide more useful results. And the tests should be selected to represent reasonable real-world scenarios. Server programs tested on otherwise idle systems and running for just a few seconds (not reaching equilibrium during the majority of the test period) are not representative at all (again: if your goal is to compare server performance). Regards, STefan
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