From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: Proposal for init/kexec/hotplug format for Xen Date: Sun, 27 Feb 2005 12:24:58 -0600 Message-ID: <4222107A.1010902@us.ibm.com> References: <1109451460.32219.11.camel@localhost.localdomain> <68d3daa4e95f4ba6740c6c0ffd3f67b8@cl.cam.ac.uk> <4221E676.5000008@us.ibm.com> <4221ED32.2010407@us.ibm.com> <260c30236e5ef2b632b85e5ebaebcb6b@cl.cam.ac.uk> <4221F26B.2030306@us.ibm.com> <1109521867.4385.22.camel@localhost> <4221F87D.2040809@us.ibm.com> <1109527920.9623.57.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit In-Reply-To: <1109527920.9623.57.camel@localhost> Sender: xen-devel-admin@lists.sourceforge.net Errors-To: xen-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: Harry Butterworth Cc: Keir Fraser , Rusty Russell , Jeremy Katz , Xen Mailing List List-Id: xen-devel@lists.xenproject.org Harry Butterworth wrote: >>We could begin work today on libxen-hcall and libxen-idc while we work >>out what the store is going to like and how the OF structure is going to >>work. Thoughts? >> >> > >The most difficult aspect of the inter-domain communication API to >express from the point of view of forwards compatibility with a >fault-tolerant implementation is that, in a fault-tolerant system with >different levels of fault tolerance, some domains will come and go >whilst others persist across failures. > > > I'm not sure fault-tolerance has to be implemented at the IDC primative level. That seems like something that's implemented at a slightly higher-level in the stack. For instance, I'm not sure how to even think about what a fault-tolerant semaphore would be however I can certainly imagine being able to implement a fault-tolerant protocol that uses semaphores and shared memory. I think fault-tolerant primatives can quite comfortably sit on top of lower-level primatives. My initial reaction is that a fault-tolerant primative is going to have a fair bit of overhead. I think the interface is going to be fairly different too. I'm not sure you want to pay the price of transparent fault-tolerance in all circumstances. It would probably be better to expect to implement a separate set of fault tolerant devices and just design the non-tolerant devices for maximum code-reuse. Regards, Anthony Liguori ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click