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Re: [Xen-devel] credit accounting question

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] credit accounting question
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 19 Jun 2008 09:04:11 +0100
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On 19/6/08 08:54, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> I recalled some post from Emmanuel to mention that split accounting
> from context switch path, to reduce overhead. System wide accouting
> may be worthy with a 30ms timer, but at least vcpu accounting can
> be carried in context switch path easily which is light enough.
> 
> Or maybe whole ticks can be removed as long as a roughly 30ms
> accounting interval is ensured by tweaking the scheduler timer. Is
> that whe you suggested?
> 
> Or was there any early experiment showing some badness if not doing
> tick based style?

I don't think the no-ticks alternative was ever implemented or measured.

We already mess with stop_timer/set_timer and calculating current system
time within the context-switch path. So we're already well set up to the
accounting on that path, imo.

 -- Keir



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