From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Gardner Subject: Re: Re: Fine-grained proxy resource charging Date: Mon, 22 Aug 2005 09:08:51 -0600 Message-ID: <4309EA83.1050001@hp.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Andi Kleen Cc: xen-devel@lists.xensource.com, John L Griffin List-Id: xen-devel@lists.xenproject.org Andi Kleen wrote: > John L Griffin writes: > > > I am looking into how to charge a domain (say, domain "A") for the > > resources consumed by other service domains (say, B) on behalf of > > A. For example, charging A for the CPU cycles consumed by the > > network I/O domain (B) as it processes packets produced or consumed > > by A. > > > Consider a xenblk request from different domains that gets merged > into a single request by the elevator. Would you charge the time the > driver spends processing that one to the one domain or the other? Or > a xenblk write the is done in the background by the pdflushd daemons? > There are lots of other cases where IO from different processes gets > "mixed" like this. And in case of Xen you would even need to track IO > from the same process. > > Not even standard linux attempts finegrained IO resource tracking and > it would be probably quite complicated and require changes all over > in the host kernel. I don't think it's a particularly good idea. It's not a bad idea just because it's a hard problem. As demonstrated in the Usenix paper that John refers to (http://www.usenix.org/publications/library/proceedings/usenix05/tech/general/cherkasova.html), the overhead in a driver domain can be very high under certain circumstances. If you have "customers" sharing domains in a virtual environment, you have to have some way of charging them fairly for resource usage. I think the Xen I/O architecture needs to account for this somehow. Rob