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From: Avi Kivity <avi@qumranet.com>
To: Paul Brook <paul@codesourcery.com>
Cc: kvm-devel <kvm-devel@lists.sourceforge.net>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] [RFC] Fix time drift of rtc clock + general support
Date: Mon, 24 Mar 2008 09:15:25 +0200	[thread overview]
Message-ID: <47E7550D.3070706@qumranet.com> (raw)
In-Reply-To: <200803232329.10474.paul@codesourcery.com>

Paul Brook wrote:
>   
>>> a new timer will be fired to try inject it again soon (==0.1msec)
>>>       
>
> If the guest is missing interrupts, the chances of a 0.1ms interval working 
> are not great.  Most likely It's either going trigger immediately, or be 
> delayed significantly and you're going to end up even further behind. 
>   

If 0.1 ms is within qemu's timeslice, then qemu should get the wakeup on 
time (assuming a host with high resolution timers).

> If triggering immediately is OK then why not do that all the time?
>   

Triggering immediately doesn't help, the guest likely has interrupts 
blocked processing the same interrupt.

> If triggering immediately is not acceptable then you're still going to loose 
> interrupts.
>   

You're still accounting for them, so if the load decreases eventually 
it's going to catch up.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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WARNING: multiple messages have this Message-ID (diff)
From: Avi Kivity <avi@qumranet.com>
To: Paul Brook <paul@codesourcery.com>
Cc: kvm-devel <kvm-devel@lists.sourceforge.net>, qemu-devel@nongnu.org
Subject: Re: [kvm-devel] [Qemu-devel] [PATCH] [RFC] Fix time drift of rtc clock + general support
Date: Mon, 24 Mar 2008 09:15:25 +0200	[thread overview]
Message-ID: <47E7550D.3070706@qumranet.com> (raw)
In-Reply-To: <200803232329.10474.paul@codesourcery.com>

Paul Brook wrote:
>   
>>> a new timer will be fired to try inject it again soon (==0.1msec)
>>>       
>
> If the guest is missing interrupts, the chances of a 0.1ms interval working 
> are not great.  Most likely It's either going trigger immediately, or be 
> delayed significantly and you're going to end up even further behind. 
>   

If 0.1 ms is within qemu's timeslice, then qemu should get the wakeup on 
time (assuming a host with high resolution timers).

> If triggering immediately is OK then why not do that all the time?
>   

Triggering immediately doesn't help, the guest likely has interrupts 
blocked processing the same interrupt.

> If triggering immediately is not acceptable then you're still going to loose 
> interrupts.
>   

You're still accounting for them, so if the load decreases eventually 
it's going to catch up.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

  reply	other threads:[~2008-03-24  7:15 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-23 14:27 [PATCH] [RFC] Fix time drift of rtc clock + general support Dor Laor
2008-03-23 14:27 ` [Qemu-devel] " Dor Laor
2008-03-23 16:19 ` Paul Brook
2008-03-23 16:19   ` Paul Brook
2008-03-23 22:40   ` Dor Laor
2008-03-23 22:40     ` Dor Laor
2008-03-23 23:29     ` Paul Brook
2008-03-23 23:29       ` Paul Brook
2008-03-24  7:15       ` Avi Kivity [this message]
2008-03-24  7:15         ` [kvm-devel] " Avi Kivity
2008-03-24  7:47         ` Avi Kivity
2008-03-24  7:47           ` [kvm-devel] " Avi Kivity
2008-03-24  7:11   ` Avi Kivity
2008-03-24  7:11     ` [kvm-devel] " Avi Kivity
2008-03-24 13:45     ` Paul Brook
2008-03-24 13:45       ` [kvm-devel] " Paul Brook
2008-03-24 13:56       ` Avi Kivity
2008-03-24 13:56         ` [kvm-devel] " Avi Kivity

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