From owner-freebsd-questions Sat Nov 6 3:32:33 1999 Delivered-To: freebsd-questions@freebsd.org Received: from funkthat.com (adsl-63-195-54-213.dsl.snfc21.pacbell.net [63.195.54.213]) by hub.freebsd.org (Postfix) with ESMTP id 5CE5214BE7 for ; Sat, 6 Nov 1999 03:32:29 -0800 (PST) (envelope-from gurney_j@efn.org) Received: (from jmg@localhost) by funkthat.com (8.9.1/8.8.7) id DAA05182; Sat, 6 Nov 1999 03:32:11 -0800 (PST) Message-ID: <19991106033211.51337@hydrogen.fircrest.net> Date: Sat, 6 Nov 1999 03:32:11 -0800 From: John-Mark Gurney To: Rob Snow Cc: freebsd-questions@freebsd.org Subject: Re: writing much slower than reading... References: <19991106013045.13836@hydrogen.fircrest.net> <38240CC0.8099D19D@lgc.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.69 In-Reply-To: <38240CC0.8099D19D@lgc.com>; from Rob Snow on Sat, Nov 06, 1999 at 05:10:56AM -0600 Reply-To: John-Mark Gurney Organization: Cu Networking X-Operating-System: FreeBSD 3.0-RELEASE i386 X-PGP-Fingerprint: B7 EC EF F8 AE ED A7 31 96 7A 22 B3 D8 56 36 F4 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Rob Snow scribbled this message on Nov 6: > Emm, I want your system. Have you double checked your numbers? They > look a bit high. Here's what I get on a vinum stripe across two 'cudas > on an SMP box: go to IBM's web site and read about the drive... I bought the drive for $241 at gogocity.com... it's a 27gig 7200rpm drive, and IBM advertises that the platter speed is 13.8meg/sec to 22meg/sec... the performance is the main reason that I bought the drive... :) also, don't forget I'm using the raw device, so there isn't any buffer like if I was going through the file system... just so you know, I went and grabed rawio to run on the disk: $ rawio -c 128 -r -w /dev/rwd0s1g Random read Sequential read Random write Sequential write ID K/sec /sec K/sec /sec K/sec /sec K/sec /sec anon 29293.9 447 28755.4 439 the -c 128 sets it for 64k transfers, and by default does 16384 transfers, so we were transfering 1gig of data... the raw partition is actually a couple gigs into the drive... and is ~25gigs large... > rsnow@basil% time dd if=/dev/vinum/rstripe of=/dev/null bs=64k > count=2048 > 2048+0 records in > 2048+0 records out > 134217728 bytes transferred in 7.938773 secs (16906609 bytes/sec) > 0.007u 0.520s 0:07.98 6.5% 73+371k 2+0io 0pf+0w > John-Mark Gurney wrote: > > > > well, I am working on writing a capture program to do 640x480x12bpp@30fps > > to a raw disk, but writing to the raw device is SOOO slow... the reason > > I say it's slow is the fact that it takes 8 times the system time writing > > than reading... > > > > a bit about the system... k6/2-250, 100mhz system bus, pc100 64meg dimm, > > VIA MVP3 chipset (IDE DMA enabled), IBM-DPTA-372730 hard disk, Hauppauge > > WinCast/TV Model 61351 B226, 3.3-RELEASE... > > > > now the hard disk can push and pull around 20meg/sec w/o any problems.. > > but when I time the disk I get: > > $ time dd if=/dev/rwd0s1g of=/dev/null bs=64k count=2048 > > 2048+0 records in > > 2048+0 records out > > 134217728 bytes transferred in 5.747521 secs (23352281 bytes/sec) > > 5.75 real 0.01 user 0.21 sys > > $ time dd if=/dev/zero of=/dev/rwd0s1g bs=64k count=2048 > > 2048+0 records in > > 2048+0 records out > > 134217728 bytes transferred in 6.281820 secs (21366057 bytes/sec) > > 6.28 real 0.00 user 1.68 sys > > > > now, why does it cost SOOO much more processing time to write than > > read?? are there plans to fix this slow down? is it possible? can't > > we just dma write out of userland since we are blocking on the write? -- John-Mark Gurney Voice: +1 408 975 9651 Cu Networking "The soul contains in itself the event that shall presently befall it. The event is only the actualizing of its thought." -- Ralph Waldo Emerson To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message