From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261879AbULPUFF (ORCPT ); Thu, 16 Dec 2004 15:05:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261957AbULPUFF (ORCPT ); Thu, 16 Dec 2004 15:05:05 -0500 Received: from mail.tmr.com ([216.238.38.203]:63249 "EHLO gatekeeper.tmr.com") by vger.kernel.org with ESMTP id S261879AbULPUE6 (ORCPT ); Thu, 16 Dec 2004 15:04:58 -0500 To: linux-kernel@vger.kernel.org Path: not-for-mail From: Bill Davidsen Newsgroups: mail.linux-kernel Subject: CD and 2.6 - more data fewer answers Date: Thu, 16 Dec 2004 15:06:16 -0500 Organization: TMR Associates, Inc Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: gatekeeper.tmr.com 1103226928 23534 192.168.12.100 (16 Dec 2004 19:55:28 GMT) X-Complaints-To: abuse@tmr.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913 X-Accept-Language: en-us, en Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org I have a 2.6.7-rc1-mm1 test system with both IDE CD and USB CD-R. Both work fine as I normally use them, the CD-R is my primary backup device. With all the discussion of DMA or not DMA, I decided to try some reads... I tried readcd using /dev/hdc and the user was 60%, sys 40%, no idle. Using ATAPI:0,0,0 I saw user 60%, sys 2% idle 38%. Then using the USB device I saw user 4%, sys 9%, idle 12%, wio 75%. The USB is much faster, so this looked right, and it appeared that on data reads DMA was being used. I have no idea where all the user CPU was going. Then I turned on -c2scan to read 2352 byte sectors without the final error correct. With /dev/hdc I saw use 42%, sys 68%. Using ATAPI:0,0,0 I saw user 47%, sys 53%. And using the USB device the c2scan ended without reading any data. The difference between /dev/hdc and ATAPI:0,0,0 is small, although consistent. The access by SCSI number failed with the USB drive, and /dev/scd0 resulted in "readcd: Invalid argument. Cannot get SCSI I/O buffer" when tried (yes, as root as well). I make no claim that this sheds light on the question, just a sprinkle of data to provide flavor. I'll bring in an audio CD tomorrow and see what trying to rip that does, unless someone beats me to it. -- -bill davidsen (davidsen@tmr.com) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me