Date: Fri, 01 Aug 2003 04:33:08 +0200 From: mh <mh@nerim.net> To: Soeren Schmidt <sos@spider.deepcore.dk>, freebsd-hackers@freebsd.org Subject: Re: Ultra ATA card doesn't seem to provide Ultra speeds. Message-ID: <3F29D164.6090904@nerim.net> In-Reply-To: <200307311219.h6VCJLVG053962@spider.deepcore.dk> References: <200307311219.h6VCJLVG053962@spider.deepcore.dk>
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Soeren Schmidt wrote: >It seems Buckie wrote: > > >>I ran a dd: >>dd if=/dev/ad1 of=/dev/zero ibs=8192 >> >>OH, you need to output to /dev/null NOT /dev/zero :) >> >> It doesn't matter as far as cdevsw entry for zero-device write leads to null_write() in /usr/src/sys/dev/null.c I was testing the memory to memory copy through a driver using /dev/null and /dev/zero and with dd if=/dev/zero of=/dev/null I get till 4.2Gb/s. Is it a maximum for memory throughout + cpu work ? (2.4GHz Laptop with SDRAM) Varying the bs parameter from 512 to 65536, I get a linear progression until bs=65536 (previous throughout) but the relative throughout is lower for bs=1024. Someone could explain?
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