Re: How to determine the backing host physical memory for a given guest ?

[Chegu Vinod <chegu_vinod@hp.com>]

On 5/9/2012 6:46 AM, Avi Kivity wrote:
> On 05/09/2012 04:05 PM, Chegu Vinod wrote:
>> Hello,
>>
>> On an 8 socket Westmere host I am attempting to run a single guest and
>> characterize the virtualization overhead for a system intensive
>> workload (AIM7-high_systime) as the size of the guest scales (10way/64G,
>> 20way/128G, ... 80way/512G).
>>
>> To do some comparisons between the native vs. guest runs. I have
>> been using "numactl" to control the cpu node&  memory node bindings for
>> the qemu instance.  For larger guest sizes I end up binding across multiple
>> localities. for e.g. a 40 way guest :
>>
>> numactl --cpunodebind=0,1,2,3  --membind=0,1,2,3  \
>> qemu-system-x86_64 -smp 40 -m 262144 \
>> <....>
>>
>> I understand that actual mappings from a guest virtual address to host physical
>> address could change.
>>
>> Is there a way to determine [at a given instant] which host's NUMA node is
>> providing the backing physical memory for the active guest's kernel and
>> also for the the apps actively running in the guest ?
>>
>> Guessing that there is a better way (some tool available?) than just
>> diff'ng the per node memory usage...from the before and after output of
>> "numactl --hardware" on the host.
>>
> Not sure if that's what you want, but there's Documentation/vm/pagemap.txt.
>

Thanks for the pointer Avi ! Will give it a try...

FYI... I tried using the recent version of the "crash" utility 
(http://people.redhat.com/anderson/) with the upstream kvm.git kernel 
(3.4.0-rc4+ ) and it seems to provides VA -> PA mappings for a given app 
on a live system.

Also looks like there is an extension to this crash utility...  called : 
qemu-vtop. which is supposed to give the GPA->HVA->HPA mappings. Need to 
give this a try...and see if it works.

Thx!
Vinod