From owner-freebsd-hackers Sat Nov 6 3:15:33 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from mw5.texas.net (mw5.texas.net [206.127.30.15]) by hub.freebsd.org (Postfix) with ESMTP id DCFE314D1F for ; Sat, 6 Nov 1999 03:15:30 -0800 (PST) (envelope-from rsnow@lgc.com) Received: from basil.dympna.COM (tcnet03-047.sat.texas.net [209.99.118.173]) by mw5.texas.net (2.4/2.4) with ESMTP id FAA18961; Sat, 6 Nov 1999 05:15:29 -0600 (CST) Received: from lgc.com (IDENT:rsnow@turbo [134.132.228.6]) by basil.dympna.COM (8.9.3/8.8.7) with ESMTP id FAA51264; Sat, 6 Nov 1999 05:15:30 -0600 (CST) (envelope-from rsnow@lgc.com) Message-ID: <38240DD0.5F89A733@lgc.com> Date: Sat, 06 Nov 1999 05:15:28 -0600 From: Rob Snow X-Mailer: Mozilla 4.7 [en] (X11; I; Linux 2.2.13 i686) X-Accept-Language: en MIME-Version: 1.0 To: John-Mark Gurney Cc: FreeBSD Hackers Subject: Re: writing much slower than reading... References: <19991106013045.13836@hydrogen.fircrest.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG John-Mark, have you double checked your numbers? I get: 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 8.096565 secs (16577120 bytes/sec) 0.016u 0.482s 0:08.09 6.0% 73+370k 0+0io 0pf+0w On vinum striped 9.1G 'cudas, SMP. -Rob 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-hackers" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message