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 09:49:51 +0100 Message-ID: <4CDA5CAF.9020003@ts.fujitsu.com> References: <4CDA5AFE.5020306@ts.fujitsu.com> <789F9655DD1B8F43B48D77C5D30659732FD7E294@shsmsx501.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <789F9655DD1B8F43B48D77C5D30659732FD7E294@shsmsx501.ccr.corp.intel.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Jiang, Yunhong" Cc: "xen-devel@lists.xensource.com" , Keir Fraser List-Id: xen-devel@lists.xenproject.org On 11/10/10 09:44, Jiang, Yunhong wrote: > > >> -----Original Message----- >> From: xen-devel-bounces@lists.xensource.com >> [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Juergen Gross >> Sent: Wednesday, November 10, 2010 4:43 PM >> To: Keir Fraser >> Cc: xen-devel@lists.xensource.com >> Subject: Re: [Xen-devel] How to detect HAP from DomU? >> >> 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. > > Will this works for Live Migration? After LM, your previous check will be invalid. (Can we migrate between system w/wo HAP?) > Or you can check after each LM. The same problem applies to a decision based on information supplied by the hypervisor. I'll have to reconsider the decision in any case, dynamical testing just takes some microseconds more, but is more flexible. 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