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RE: [Xen-devel] [PATCH]Add free memory size of every NUMA node in phsica

To: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH]Add free memory size of every NUMA node in phsical info
From: "Duan, Ronghui" <ronghui.duan@xxxxxxxxx>
Date: Tue, 26 Feb 2008 11:39:38 +0800
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Thread-topic: [Xen-devel] [PATCH]Add free memory size of every NUMA node in phsical info
Thanks for your advice.

As far as I know, xc_availheap will return specific node's free memory,
in this context we need all nodes' info, so under the most conditions if
use xc_availheap, there may be 4~8 times hypercall, one time per node.
So in my methods, I allocate more memory to let one hpercall to return a
list instead of a value. It is something related with time complexity
and space complexity. This info has the same attribute with
"cpu_to_node" in physical info. So I think it is better to get them
using the same methods.

Thanks again.

>-----Original Message-----
>From: Daniel P. Berrange [mailto:berrange@xxxxxxxxxx]
>Sent: Tuesday, February 26, 2008 11:02 AM
>To: Duan, Ronghui
>Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: Re: [Xen-devel] [PATCH]Add free memory size of every NUMA node
>phsical info
>On Tue, Feb 26, 2008 at 10:46:17AM +0800, Duan, Ronghui wrote:
>> I see that, the reason I don't use that function is there need one
>> time hypercall, I only reuse the function which have been realized in
>> hypervisor. Thanks for your advice.
>The performance impact of doing 1 extra hypercall for 'availheap' is
>completely irrelevant in this context. The time for 1 extra hypercall
>is dwarfed (by several orders of magnitude) by the overhead due to
>'xm' and 'xend' being in python & using XML-RPC. We should just use
>the existing hypercall & not worry about time overhead we'll never
>|=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392
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