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] System time monotonicity

To: John Levon <levon@xxxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] System time monotonicity
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Mon, 26 Mar 2007 19:47:49 +0100
Delivery-date: Mon, 26 Mar 2007 11:45:43 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <20070326182323.GA30728@xxxxxxxxxxxxxxxxxxxxxxx>
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>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: Acdv10BAfqm0htvKEdu/NgAWy6hiGQ==
Thread-topic: [Xen-devel] System time monotonicity
User-agent: Microsoft-Entourage/
On 26/3/07 19:23, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

>> From what I can work out, time is supposed to be monotonic but I admit I
> can't really understand the time code yet at least. I couldn't find any
> documentation on what to expect from system time. Any suggestions?
> This seems to happen across all the hardware we've tried but this
> particular case is a Sun V20Z with two CPUs:
>   x86 (AuthenticAMD family 15 model 5 step 10 clock 2392 MHz)
>         AMD Opteron(tm) Processor 250

Small backwards time deltas are possible from the current time code. You'll
have to filter them out yourself if you can't deal with them. We could add
extra code in Xen to stop this happening for any individual VCPU.

 -- Keir

Xen-devel mailing list