From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Loopback Performance (Was Re: Disk naming) Date: Fri, 15 Apr 2005 19:12:23 -0500 Message-ID: <42605867.30202@us.ibm.com> References: <42603C24.8060303@us.ibm.com> <200504160029.15936.mark.williamson@cl.cam.ac.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200504160029.15936.mark.williamson@cl.cam.ac.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Mark Williamson Cc: Ian Pratt , xen-devel@lists.xensource.com, Adam Heath List-Id: xen-devel@lists.xenproject.org Mark Williamson wrote: >On Friday 15 April 2005 23:11, Anthony Liguori wrote: > > >I'm sorry but I don't follow this. The inodes for the filesystem inside it >only need to be looked up by the guest filesystem driver. The inode for the >disk file only needs to be looked up once in dom0 when the file is opened >(the metadata will then be cached). Am I missing something? > > I meant looking up the data blocks in the inode. You may be hitting triple-indirect blocks twice. I don't know enough about the kernel level caching to say anything definitive. I do have some ideas who to ask though. Regards, Anthony Liguori >The data you've collected are interesting though. I wonder if searching the >LKML archives might yield any interesting discussion about the loop device's >behaviour. > >Cheers, >Mark > >