Date: Sun, 26 Sep 2004 20:15:29 -0700 From: John-Mark Gurney <gurney_j@resnet.uoregon.edu> To: Mauro Triulzi <triulzi@freesurf.ch> Cc: =?iso-8859-1?Q?S=F8ren?= Schmidt <sos@DeepCore.dk> Subject: Re: ATA disk performance (ICH2 controller), some testsandcomparison with Linux 2.6.5 Message-ID: <20040927031529.GA22681@funkthat.com> In-Reply-To: <41575CCB.40107@freesurf.ch> References: <20040926044943.I40616-100000@mxb.saturn-tech.com> <200409261332.23227.michaelnottebrock@gmx.net> <4156B234.1090603@DeepCore.dk> <41575CCB.40107@freesurf.ch>
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Mauro Triulzi wrote this message on Mon, Sep 27, 2004 at 02:20 +0200:
> ii) Now I tried a fair raw throughput comparison between Linux and
> FreeBSD. This time I read always the same whole (Linux) partition
> (~4GB) so that the results should be comparable. I always used native
> dd (FreeBSD and Linux). A measure with Linux dd under emulation
> in FreeBSD gave yet the same result:
>
> dd if=/dev/ad0s9 bs=nnn of=/dev/null
> FreeBSD:
> nnn=4k: 4301789184 bytes transferred in 170.031898 secs (25299895
> bytes/sec)
> nnn=8k: 4301789184 bytes transferred in 114.446100 secs (37587905
> bytes/sec)
> nnn=16k: 4301789184 bytes transferred in 87.794076 secs (48998627
> bytes/sec)
> nnn=64k: 4301789184 bytes transferred in 89.515195 secs (48056525
> bytes/sec)
> nnn=512k: 4301789184 bytes transferred in 90.357666 secs (47608458
> bytes/sec)
> (no significant changes before or after reinit)
>
> Linux:
> nnn=4k: 4301789184 bytes transferred in 93 secs (~46 Mbytes/sec)
> nnn=8k: 4301789184 bytes transferred in 86 secs (~50 Mbytes/sec)
> nnn=16k: 4301789184 bytes transferred in 90 secs (~48 Mbytes/sec)
> nnn=64k: 4301789184 bytes transferred in 95 secs (~45 Mbytes/sec)
> nnn=512k: 4301789184 bytes transferred in 92 secs (~47 Mbytes/sec)
>
> I notice, that the rates are very similar if bs >= 16k. Under FreeBSD
> the raw throughput rate depends on the block size. Read rate under Linux
> is independent of the block size. Is there a special reason for that?
Last I heard Linux did not have a raw device.. this means that it will
always be cached, and will do various read-ahead optimizations, while
FreeBSD does not have a buffered/cooked device anymore.. w/o the cooked
device FreeBSD has to suffer the latency of the command to the drive...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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