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] RE: rdtsc: correctness vs performance on Xen (and KVM?)

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 02 Sep 2009 22:50:23 +0100
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Wed, 02 Sep 2009 14:51:27 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4A9EE74F.1000605@xxxxxxxx>
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: AcosFpqJQdmiVkilRfOnOUrmevAtGAAAMTfM
Thread-topic: [Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)
User-agent: Microsoft-Entourage/12.20.0.090605
On 02/09/2009 22:44, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:

> On 09/02/09 00:20, Keir Fraser wrote:
>> The problem is a bit easier with vsyscall potentially. For example, give
>> each thread its own vsyscall clock data area (easy?), updated by kernel
>> whenever the thread is scheduled, and increment a version counter, checked
>> before and after by the vsyscall operation.
>>   
> 
> Yes.  Perhaps the very simplest way would be to make the kernel update
> the pvclock version counter on context switch, the same way Xen does;
> that would allow the usermode vsyscall code to use exactly the same
> algorithm as the kernel code.  Would Xen cope with that?

Yes, that's basically how I would envision it working. The main missing
detail afaics is how to manage and access the required per-thread data.

 -- Keir



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

<Prev in Thread] Current Thread [Next in Thread>