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/
Home Products Support Community News


Re: [Xen-devel] Regarding page table management changes from Xen v1 to X

To: Himanshu Raj <rhim@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Regarding page table management changes from Xen v1 to Xen v2 (and v3)
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 26 Apr 2006 17:18:28 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Wed, 26 Apr 2006 09:22:27 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <20060426153556.GB27766@xxxxxxxxxxxxx>
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/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <20060426153556.GB27766@xxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

On 26 Apr 2006, at 16:35, Himanshu Raj wrote:

I am trying to understand the rationale behind this change. In previous case, there would be no page faults due to page table updates and only one hypercall. In the second case, there would be atleast 2 page faults due to PT management activity, but no hypercalls. Besides, mapping and remapping with different permissions imply removing this entry from TLB (which is hopefully being done with invlpg). Benefit of latter approach only seems to be the removal of xen specific linux code. Why was the approach changed? Could someone please shed some light on

It's useful for batched updates (e.g., fork()) where the 2 faults are amortised across up to 1024 pte changes.

 -- Keir

Xen-devel mailing list