From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: How to detect HAP from DomU? Date: Wed, 10 Nov 2010 09:42:38 +0100 Message-ID: <4CDA5AFE.5020306@ts.fujitsu.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: Keir Fraser Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 11/10/10 09:36, Keir Fraser wrote: > On 10/11/2010 08:22, "Juergen Gross" wrote: > >> is there any way for a HVM-domain to detect whether it is running with HAP >> enabled? I couldn't find any interface for this information. >> >> Background: in our BS2000 domain (HVM with PV-drivers) we sometimes have to >> copy complete pages between kernel and user. An alternative to the copy >> would be a remapping of the page. The remap is faster than the copy with HAP >> enabled, but much slower without HAP. So it would be best to copy without HAP >> and remap with HAP. > > You could do a few remaps and copies and see how long it takes? Has the > advantage that you aren't tied up to one policy based on one system's > timings for those particuler ops. I don't think basing policy on static > assumptions about hidden implementation features is a good idea. Okay, that's a good idea. I'm going this way. Thanks, Juergen -- Juergen Gross Principal Developer Operating Systems TSP ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@ts.fujitsu.com Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html