Date: Wed, 27 Oct 2010 11:54:07 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-performance@freebsd.org Subject: Re: Possible evidence of performance regression for 8.1-S (vs. 7.1) Message-ID: <ia8srt$th0$1@dough.gmane.org> In-Reply-To: <20101026174501.GH2262@albert.catwhisker.org> References: <20101020174854.GZ21226@albert.catwhisker.org> <20101021215330.GA86224@dan.emsphone.com> <20101021224237.GG52404@albert.catwhisker.org> <4CC6C396.1010905@freebsd.org> <20101026121352.GC2262@albert.catwhisker.org> <AANLkTi=Q9EwPJ%2BC4n3UFF9uFtNsukntkmqSjrXsHE3cm@mail.gmail.com> <20101020174854.GZ21226@albert.catwhisker.org> <20101021215330.GA86224@dan.emsphone.com> <20101021224237.GG52404@albert.catwhisker.org> <4CC6C396.1010905@freebsd.org> <20101026174501.GH2262@albert.catwhisker.org>
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On 10/26/10 19:45, David Wolfskill wrote: > On Tue, Oct 26, 2010 at 02:03:34PM +0200, Ivan Voras wrote: >> ... >> Since you now have the two kernels readily available, can you rule out >> NFS by just repeating the step which involves it in both kernels and >> compare the results? > > On Tue, Oct 26, 2010 at 02:47:11PM +0200, Ivan Voras wrote: >> ... >> Couldn't you simply run blogbench or just copy/untar a full /usr/ports >> tree on NFS that while booting either of the kernels? > > OK; here are timing results from 5 iterations each of running "tar > xf", reading aa gzipped tarball of /usr/ports (updated earlier this > morning) from NFS & writing it to the same local file system that > I used for the previously-cited builds. Each of these was run on > the 8.x reference machine, and each terminated with a status code of 0: > > start stop real user sys os > 1288111167 1288111298 131.14 12.77 17.88 7.1-R+ > 1288109542 1288109653 111.26 12.03 14.88 8.1-S [7.1-R+ userland] > 1288112673 1288112768 94.88 9.41 12.87 8.1-S There's a slight problem here: 8.1 with 7.1 userland should, in this test, behave the same as 8.1 with 8.1 userland. There have been no breakthroughs in gzip decompression or compiler optimization between those two releases that would make 8.1 userland faster. The most probable cause for the difference is simply disk drive location - inner vs outer tracks (you can run diskinfo -vt on the drive - it's non-destructive). This may also be the cause for your originally noticed speed difference. You could try some IO tuning on the box with sysctls like: vfs.hirunningspace=8388608 vfs.lorunningspace=6291456 vfs.ufs.dirhash_maxmem=8388608 vfs.read_max=32 ... but if the problem is due to the disk track locations, it's not really a problem.
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