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Re: [Xen-devel] Regarding page table management changes from Xen v1 to X

To: Himanshu Raj <rhim@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Regarding page table management changes from Xen v1 to Xen v2 (and v3)
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 26 Apr 2006 17:18:28 +0100
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On 26 Apr 2006, at 16:35, Himanshu Raj wrote:

I am trying to understand the rationale behind this change. In previous case, there would be no page faults due to page table updates and only one hypercall. In the second case, there would be atleast 2 page faults due to PT management activity, but no hypercalls. Besides, mapping and remapping with different permissions imply removing this entry from TLB (which is hopefully being done with invlpg). Benefit of latter approach only seems to be the removal of xen specific linux code. Why was the approach changed? Could someone please shed some light on
this?

It's useful for batched updates (e.g., fork()) where the 2 faults are amortised across up to 1024 pte changes.

 -- Keir


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