Home » Mailing list archives » linux-kernel » 2007 » October » 29

Re: [PATCH] raise tsc clocksource rating

!MAILaRCHIVE_VOTE_RePLACE
Previous message: [thread] [date] [author]
Next message: [thread] [date] [author]
[view in full thread]
From: Dan Hecht <dhecht@...>
To: Ingo Molnar <mingo@...>
Cc: Zachary Amsden <zach@...>, Glauber de Oliveira Costa <gcosta@...>, <linux-kernel@...>, <tglx@...>, <rusty@...>, <jeremy@...>, <--cc@...>, <avi@...>, <kvm-devel@...>, Glauber de Oliveira Costa <glauber@...>, Garrett Smith <garrett@...>
Subject: Re: [PATCH] raise tsc clocksource rating
Date: Monday, October 29, 2007 - 7:24 pm

On 10/29/2007 04:02 PM, Ingo Molnar wrote:

Not really.  In the case hardware TSC is perfect, the paravirt time 
counter can be implemented directly in terms of hardware TSC; there is 
no loss in optimization.  This is done transparently.  And virtual TSC 
can be implemented this way too.

The real improvement that a paravirt clocksource offers over the TSC 
clocksource is that the guest does not need to measure the TSC frequency 
itself against some other constant frequency source (which is 
problematic on a virtual machine).  Instead, the paravirt clocksource 
queries the hypervisor for the frequency of the counter.  As you know, 
with clocksource style kernels, it's important to get this frequency 
correct, or else the guest will have long-term time drift.


-
Previous message: [thread] [date] [author]
Next message: [thread] [date] [author]
Messages in current thread:
[PATCH] raise tsc clocksource rating, Glauber de Oliveira Costa..., (Mon Oct 29, 7:10 pm)
Re: [PATCH] raise tsc clocksource rating, H. Peter Anvin, (Mon Oct 29, 8:17 pm)
Re: [PATCH] raise tsc clocksource rating, Zachary Amsden, (Mon Oct 29, 6:42 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 6:48 pm)
Re: [PATCH] raise tsc clocksource rating, Zachary Amsden, (Mon Oct 29, 6:55 pm)
Re: [PATCH] raise tsc clocksource rating, Glauber de Oliveira Costa..., (Tue Oct 30, 7:59 am)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 7:02 pm)
Re: [PATCH] raise tsc clocksource rating, Dan Hecht, (Mon Oct 29, 7:24 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Tue Oct 30, 3:14 am)
Re: [kvm-devel] [PATCH] raise tsc clocksource rating, Avi Kivity, (Tue Oct 30, 12:24 am)
Re: [PATCH] raise tsc clocksource rating, Zachary Amsden, (Mon Oct 29, 7:13 pm)
Re: [PATCH] raise tsc clocksource rating, Glauber de Oliveira Costa..., (Tue Oct 30, 8:02 am)
Re: [PATCH] raise tsc clocksource rating, Zachary Amsden, (Tue Oct 30, 1:58 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 7:17 pm)
Re: [PATCH] raise tsc clocksource rating, Jeremy Fitzhardinge, (Mon Oct 29, 6:52 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 6:55 pm)
Re: [PATCH] raise tsc clocksource rating, Jeremy Fitzhardinge, (Mon Oct 29, 7:17 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 7:21 pm)
Re: [PATCH] raise tsc clocksource rating, Jeremy Fitzhardinge, (Mon Oct 29, 7:33 pm)
Re: [PATCH] raise tsc clocksource rating, Jeremy Fitzhardinge, (Mon Oct 29, 6:45 pm)
Re: [PATCH] raise tsc clocksource rating, Thomas Gleixner, (Mon Oct 29, 6:17 pm)
Re: [PATCH] raise tsc clocksource rating, Rusty Russell, (Mon Oct 29, 10:39 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Tue Oct 30, 3:37 am)
Re: [PATCH] raise tsc clocksource rating, Glauber de Oliveira Costa..., (Tue Oct 30, 8:13 am)
Re: [PATCH] raise tsc clocksource rating, Rusty Russell, (Tue Oct 30, 6:52 am)
Re: [PATCH] raise tsc clocksource rating, john stultz, (Mon Oct 29, 9:26 pm)
Re: [PATCH] raise tsc clocksource rating, Ingo Molnar, (Mon Oct 29, 6:36 pm)