RE: [Xen-devel] [PATCH] fix memory allocation from NUMA node for VT-d.

["Kay, Allen M" <allen.m.kay@xxxxxxxxx>]

>Xen's user will assign a device to a closer guest. So, node of the
>guest and node connected to IOMMU will be the same.
>As a result, the memory performance will be improved with my patch. 

Are you assuming guest will ping the guest to a physical CPU?  How does the 
user figure out which devices are closer to which physical CPU in the platform 
in a QPI system without using proximity domain info?

Allen

>-----Original Message-----
>From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
>[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
>Yuji Shimada
>Sent: Wednesday, November 19, 2008 12:26 AM
>To: Espen Skoglund
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; 'Keir Fraser'
>Subject: Re: [Xen-devel] [PATCH] fix memory allocation from 
>NUMA node for VT-d.
>
>Hi Espen,
>
>Your suggestion allocating memory from one of the nodes where the
>IOMMU is attached improves performance more. But more memory is
>needed, because structures are needed per IOMMU.
>
>My patch keeps the current implementation, one Device Assignment
>Structure and Address Translation Structure per guest.
>
>Xen's user will assign a device to a closer guest. So, node of the
>guest and node connected to IOMMU will be the same.
>As a result, the memory performance will be improved with my patch.
>
>Thanks,
>--
>Yuji Shimada
>
>On Tue, 18 Nov 2008 12:00:37 +0000
>Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx> wrote:
>
>> Given an FSB based system the IOMMUs sit in the north-bridge.  How
>> does this work qith QPI?  Where in the system do the different IOMMUs
>> sit?  Wouldn't it make more sense to allocate memory from one of the
>> nodes where the IOMMU is attached?  Having the memory allocated from
>> the node of the guest only helps when the guest needs to update its
>> page tables.  I'd rather optimize for page table walks in the IOMMU.
>> 
>>      eSk
>
>
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