From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Gardner Subject: Scheduling of I/O domains Date: Wed, 21 Jul 2004 11:21:29 -0600 Sender: xen-devel-admin@lists.sourceforge.net Message-ID: <40FEA619.1050800@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: xen-devel@lists.sourceforge.net List-Id: xen-devel@lists.xenproject.org I have been looking for the code in xen that handles scheduling of I/O domains, but have not succeeded in finding any. Only after some time did I start thinking that maybe there wasn't any. So I did the following simple experiment: In domain 1: time dd if=/dev/hda of=/dev/null bs=1024k count=100 and this this took about 2 seconds. Then I ran a cpu-consuming process in domain 2, and repeated the dd command above. The result was more than 8 seconds! This strongly suggests that domain 0 is not being treated specially by the scheduler, and is being made to wait before servicing I/O interrupts, thereby killing I/O performance in the presence of cpu-bound domain activity. It seems to me that I/O domains need to be scheduled and dispatched immediately upon receipt of an I/O interrupt. Am I missing something here? How come nobody has noticed this behavior before? Is somebody working on this? I Rob Gardner ------------------------------------------------------- This SF.Net email is sponsored by BEA Weblogic Workshop FREE Java Enterprise J2EE developer tools! Get your free copy of BEA WebLogic Workshop 8.1 today. http://ads.osdn.com/?ad_id=4721&alloc_id=10040&op=click