Date: Fri, 23 May 1997 23:14:52 +1000 From: Bruce Evans <bde@zeta.org.au> To: current@FreeBSD.ORG, sos@sos.freebsd.dk Subject: Re: cd9660 filesystem slowed down ??? Message-ID: <199705231314.XAA27893@godzilla.zeta.org.au>
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>I have this strange observation under 3.0-current: > >dd if=/dev/wcd0c of=/dev/null gives about 2MB/sec > >Mount the CD and then > >dd if=somefile of=/dev/null gives about 70K/sec > >Doing the same on 2.2.2 gives 2MB/sec / 1800K/sec... > >What have we done to degrade cd9660 performance that much ???? The first dd has the common error of operating on the block device instead of the raw device. This gives a effective block size of 2K instead of the size requeseted by dd (512). 2K happens to work well for wcd0. I get almost 1200K/s for an 8x drive. dd if=/dev/rwcd0c of=/dev/null gives a kernel printf "atapi0.1: invalid data direction", a flashing wcd0 LED and a hung IDE controller here. The second dd uses the too-small block size of 512. Apparently read-ahead doesn't work for too-small block sizes in -current. I get 50K/sec for a block size of 512 and almost 1200K/sec for a block size of 2K. Check rev.1.28 of cd9600_vnops.c and the Lite2 changes. Not much else has changed. Bruce
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