| |
|
 |
|
 |
|
|
|
| |
|
|
xen-devel
RE: [Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL
|
To: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
|
Subject: |
RE: [Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL |
|
From: |
"Tian, Kevin" <kevin.tian@xxxxxxxxx> |
|
Date: |
Wed, 5 Aug 2009 13:35:45 +0800 |
|
Accept-language: |
en-US |
|
Acceptlanguage: |
en-US |
|
Cc: |
Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>, Levon <levon@xxxxxxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, John, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> |
|
Delivery-date: |
Tue, 04 Aug 2009 22:37:03 -0700 |
|
Envelope-to: |
www-data@xxxxxxxxxxxxxxxxxxx |
|
In-reply-to: |
<4A78CCDD.9090205@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> |
|
References: |
<C68F298A.104C0%keir.fraser@xxxxxxxxxxxxx> <4A78CCDD.9090205@xxxxxxxx> |
|
Sender: |
xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
|
Thread-index: |
AcoVYI0nnN88UD3ETQuxEMRXQ3nhQgALTjSw |
|
Thread-topic: |
[Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL |
>From: Jeremy Fitzhardinge
>Sent: 2009年8月5日 8:06
>
>On 07/24/09 01:04, Keir Fraser wrote:
>> Okay, so the issue you are worried about is not specific to
>Xen. So how is
>> native Linux tackling this, for example?
>>
>
>Linux will use the tsc where possible, but regularly assesses its
>perceived accuracy and will move to a different clocksource if the tsc
>appears to the playing up. I don't think it ever assumes the tsc is
>synced between CPU/cores.
It cares. See tsc_sync.c under x86 arch, where unsynced warps
mark tsc as unstable.
Thanks,
Kevin
>
>It allows rdtsc from usermode, but it is generally considered
>to be very
>buggy and ill-defined behaviour. It makes no attempt to make usermode
>rdtsc in any way meaningful. The exception is the vgettimeofday
>vsyscall which does Xen-like timekeeping, in which it gets the tsc,cpu
>tuple atomically, then scales it with timing parameters from
>the kernel.
>
> J
>
>_______________________________________________
>Xen-devel mailing list
>Xen-devel@xxxxxxxxxxxxxxxxxxx
>http://lists.xensource.com/xen-devel
> _______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
| |
|
Home