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Re: [Xen-devel][PATCH] don't split the whole large page while live migra

To: "Xin, Xiaohui" <xiaohui.xin@xxxxxxxxx>
Subject: Re: [Xen-devel][PATCH] don't split the whole large page while live migration with EPT
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Thu, 16 Apr 2009 13:35:55 +0100
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At 13:33 +0100 on 16 Apr (1239888814), Xin, Xiaohui wrote:
> Before, when HVM guest live migration with EPT, we just write protect all the 
> EPT leaf entries.
> Then we know the dirty pages through ept_handle_violation(), and call 
> p2m_change_type()
> to put back the write access of the EPT entries. At that time when we use 
> large pages,
> we used to split the large page to 4K.
> It?s not necessary. Alternatively, we can just retain the large page entries,
> and put back the write access and mark dirty all the small pages in the large 
> page.
> The patch attached removes the splitting.

What effect does this have on live migration time/traffic under load?



Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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