linux-kernel - Re: [PATCH v6 04/12] Add memory slot versioning and use it to provide fast guest write interface

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Message-ID: <20101007172318.GC2397@redhat.com>
Date:	Thu, 7 Oct 2010 19:23:18 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Gleb Natapov <gleb@...antech.com>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
	riel@...hat.com, cl@...ux-foundation.org
Subject: Re: [PATCH v6 04/12] Add memory slot versioning and use it to
 provide fast guest write interface

On Thu, Oct 07, 2010 at 06:20:53PM +0200, Avi Kivity wrote:
>  On 10/07/2010 06:03 PM, Gleb Natapov wrote:
> >>  >
> >>  >  Isn't SET_USER_MEMORY_REGION so slow that calling it 2^32 times
> >>  >  isn't really feasible?
> >>
> >>  Assuming it takes 1ms, it would take 49 days.
> >>
> >We may fail ioctl when max value is reached. The question is how much slot
> >changes can we expect from real guest during its lifetime.
> >
> 
> A normal guest has a 30 Hz timer for reading the vga framebuffer,
> multiple slots.  Let's assume 100 Hz frequency, that gives 490 days
> until things stop working.
> 
And reading vga framebuffer needs slots changes because of dirty map
tracking?

--
			Gleb.
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