Date: Thu, 21 Dec 2006 23:22:38 +1300 From: Mark Kirkwood <markir@paradise.net.nz> To: Pieter de Goeje <pieter@degoeje.nl> Cc: freebsd-stable@freebsd.org Subject: Re: Cached file read performance with 6.2-PRERELEASE Message-ID: <458A606E.6080008@paradise.net.nz> In-Reply-To: <200612201536.25497.pieter@degoeje.nl> References: <45888C68.10305@paradise.net.nz> <200612200816.51043.joao@matik.com.br> <4589128F.9030404@paradise.net.nz> <200612201536.25497.pieter@degoeje.nl>
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Pieter de Goeje wrote: > On Wednesday 20 December 2006 11:38, Mark Kirkwood wrote: >> In fact if you note that the PIII HW *can* actually do 700MB/s, it >> suggests that your HW is capable of considerably more than 900MB/s - >> given that opteron's have excellent cpu to memory bandwidth, and the >> speed of your memory! > Indeed! > Copying /dev/zero to /dev/null yields more than 5GB/sec on a simple 2Ghz > Athlon64. It imagine there are quite a few extra things done when copying a > file from cache, because I can only manage to get one fifth (~1GB/sec) of the > theoretical speed. (this is with a file that fills more than half of all > memory) > Fascinating, never thought of trying that! On my 2 (essentially) identical PIII systems, doing copy /dev/zero to /dev/null yields 4.1 GB/s (Gentoo) and 2.0GB/s (FreeBSD) - so yeah, clearly both do something special in that case... (growl... we - i.e FreeBSD - seem to be slower again...tho at that sort of rate, who cares!) Cheers Mark
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