Date: Fri, 1 Aug 2003 10:15:03 +0200 From: Ruben de Groot <mail23@bzerk.org> To: mh <mh@nerim.net> Cc: freebsd-hackers@freebsd.org Subject: Re: Ultra ATA card doesn't seem to provide Ultra speeds. Message-ID: <20030801081503.GA66987@ei.bzerk.org> In-Reply-To: <3F29D164.6090904@nerim.net> References: <200307311219.h6VCJLVG053962@spider.deepcore.dk> <3F29D164.6090904@nerim.net>
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On Fri, Aug 01, 2003 at 04:33:08AM +0200, mh typed: > 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) The following comparison is probably bogus, but can anybody explain the huge difference? 1) FreeBSD 4.8-STABLE, 2x 1Ghz PIII, 512MB Memory bsdbox> dd if=/dev/zero of=/dev/null bs=1m count=10000 10000+0 records in 10000+0 records out 10485760000 bytes transferred in 23.482885 secs (446527758 bytes/sec) 2) Linux 2.4.21, 1x 2.6Ghz PIV, 512 MB Memory linbox> dd if=/dev/zero of=/dev/null bs=1M count=10000 10000+0 records in 10000+0 records out 10485760000 bytes transferred in 0.308408 seconds (33999639291 bytes/sec) -Ruben > 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? > > > > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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