From mboxrd@z Thu Jan 1 00:00:00 1970 From: Harry Butterworth Subject: Re: Why are I/O rings bidirectional? Date: Mon, 07 Feb 2005 23:52:57 +0000 Message-ID: <1107820377.7818.30.camel@localhost> References: <200502072300.09635.maw48@cl.cam.ac.uk> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit In-Reply-To: <200502072300.09635.maw48@cl.cam.ac.uk> 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: Mark Williamson Cc: xen-devel@lists.sourceforge.net, McGroarty List-Id: xen-devel@lists.xenproject.org I think the intended question was "why have both requests and responses in the same ring rather than have two rings, one for requests and one for responses?" On Mon, 2005-02-07 at 23:00 +0000, Mark Williamson wrote: > > Hello. I am reading Xen and the Art of Virtualization. I am curious as > > to why the async I/O ring buffers contain both requests and responses > > in the same ring. > > Requests contain details of the IO to be done. Responses notify the domain > when the IO is complete and whether it was successful or not. > > Requests can complete out of order, so it's necessary to have response > messages following back to the domain to tell it when each request is done. > If the requests were always dealt with in order it would not be necessary to > have responses flowing back, so the ring could be unidirectional. > > The Safe Hardware Access paper has more details about the IO rings work. > > HTH, > Mark > > > ------------------------------------------------------- > 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 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/xen-devel -- Harry Butterworth ------------------------------------------------------- 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