Date: Fri, 23 May 1997 09:41:01 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: bde@zeta.org.au (Bruce Evans) Cc: current@FreeBSD.ORG, sos@sos.freebsd.dk Subject: Re: cd9660 filesystem slowed down ??? Message-ID: <199705231641.JAA07418@phaeton.artisoft.com> In-Reply-To: <199705231314.XAA27893@godzilla.zeta.org.au> from "Bruce Evans" at May 23, 97 11:14:52 pm
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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. Ah. Well. We should all remember to not use 2k blocks on a CDROM instead of 512b (or the native size, 1k) because then we will get 2MB/sec, and that's (somehow???) undesirable. 8-| > 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. There seems to be a lot of that going around on character devices these days... 8-(. > 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. Try 1K, the native size. I think you are seeing pessimal rotational latency. Regards, Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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