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Re: [Xen-devel] sparse M2P table

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] sparse M2P table
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Thu, 17 Sep 2009 09:02:01 +0100
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On 17/09/2009 08:28, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

>> The only structure in Xen that I think doesn't just work with
>> expanding its virtual memory allocation and sparse-mapping is the '1:1
>> memory mapping'.
>> Because to address such large sparse memory maps, the virtual memory
>> allocation would be too large. So I'm guessing the '1:1 memory
>> map' area
>> will end up divided into say 1TB strips with phys_to_virt() executing
>> a radix-tree lookup to map physical address ranges onto those
>> dynamically-allocated strips.
> 
> Yes, and the strip size maybe dynamic determined.
> 
> Also if we will always keep the 1:1 memory mapping for all memory? Currently
> we have at most 5TB  virtual address for the 1:1 mapping, hopefully it will
> work for most system now.

Yeah, I think 5TB will just about do us for now. ;-) After all, I think the
biggest machine Xen has been tested on so far is 256GB.

 -- Keir



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