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: [PATCH 3/5] x86/pvclock: add vsyscall implementation

To: Avi Kivity <avi@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 3/5] x86/pvclock: add vsyscall implementation
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 15 Oct 2009 12:17:31 -0700
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, kurt.hackel@xxxxxxxxxx, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Glauber de Oliveira Costa <gcosta@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Zach Brown <zach.brown@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Chris Mason <chris.mason@xxxxxxxxxx>
Delivery-date: Thu, 15 Oct 2009 12:17:56 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4AD5C4ED.3050809@xxxxxxxxxx>
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>
References: <1254790211-15416-1-git-send-email-jeremy.fitzhardinge@xxxxxxxxxx> <1254790211-15416-4-git-send-email-jeremy.fitzhardinge@xxxxxxxxxx> <4ACB0833.2050203@xxxxxxxxxx> <4ACB9074.1000804@xxxxxxxx> <4ACC6C9C.7080707@xxxxxxxxxx> <4ACFD43E.6000506@xxxxxxxx> <4AD0CDFB.9030704@xxxxxxxxxx> <4AD3738B.6050200@xxxxxxxx> <4AD375A5.8050205@xxxxxxxxxx> <4AD37FE3.1010002@xxxxxxxx> <4AD420A4.7050508@xxxxxxxxxx> <4AD4DC52.8090508@xxxxxxxx> <4AD5C4ED.3050809@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-2.7.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4
On 10/14/09 05:32, Avi Kivity wrote:
> On 10/14/2009 05:00 AM, Jeremy Fitzhardinge wrote:
>>
>>> So it's broken or disabled when that assumption is wrong?  We could
>>> easily fix that now.  Might even reuse the pvclock structures.
>>>      
>> Well, the kernel internally makes more or less the same assumption; the
>> vsyscall clocksource is the same as the kernel's internal one.  I think
>> idea is that it just drops back to something like hpet if the tsc
>> doesn't have very simple SMP characteristics.
>>
>> If the kernel could characterize the per-cpu properties of the tsc more
>> accurately, then it could use the pvclock mechanism on native.
>>    
>
> It does - that's how kvm implements pvclock on the host side.  See
> kvmclock_cpufreq_notifier() in arch/x86/kvm/x86.c.

The tsc clocksource currently seems a fair bit more picky though; it
doesn't attempt to sync tscs or work out their relative offsets or
rates.  Which seems a bit defeatist.

    J

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

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