WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] How to detect HAP from DomU?

To: Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] How to detect HAP from DomU?
From: Keir Fraser <keir@xxxxxxx>
Date: Wed, 10 Nov 2010 08:36:15 +0000
Cc:
Delivery-date: Wed, 10 Nov 2010 00:37:12 -0800
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:user-agent:date :subject:from:to:message-id:thread-topic:thread-index:in-reply-to :mime-version:content-type:content-transfer-encoding; bh=j6BxCjS+xEtj15cleS6b2fTaRAXHWo9uwU1y3SDx3pQ=; b=hmp0GGe31rViPW8KXac1nLdzoi98POPX+3SAs8SQ1pf0xN2IO6Kr5uZdnONSgxghuV v/lNAsyDRtKjI5BeVbw3csQ+TcvXLhX4SDpvIpztBdPejkF43izcuBZtRtkQGwq/l7k5 S8Cu8W71XeMrDFjXh0WfdL74qhDlObtvqQ0o8=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:user-agent:date:subject:from:to:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=gcDhFb4kyBMaX/ngtMSVWPkzLMWpZasuZhq9CB9ggwueKVpK1XkkI7M4K1EMsT+lAu tPKuhYM0Qe4RhWRXPLs2Jz6N9yfy+pjyPrguN2iFS7e0i6qfDqJdRGvUqattVWWz8mFM BDAQKJQuVr/NaNA2GPDwuFfBvz28XSH4JZBXo=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4CDA565A.5040804@xxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcuAslZDFbTkpzt0R0a27Ncti5+M2Q==
Thread-topic: [Xen-devel] How to detect HAP from DomU?
User-agent: Microsoft-Entourage/12.27.0.100910
On 10/11/2010 08:22, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> 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.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel