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xen-devel
RE: [Xen-devel] Memory overhead of HVM domains
>From you definition of overhead, I think your overhead should include the
>shadow page table, p2m table and those shadow cache, am I right?
Not sure if any other sources.
Also I just find a bug on qemu, which may occupy double size of the video
memory if you are using Xwindow.
Thanks
Yunhong Jiang
---Original Message-----
>From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Charles Coffing
>Sent: 2006年4月11日 12:43
>To: xen-devel@xxxxxxxxxxxxxxxxxxx
>Subject: [Xen-devel] Memory overhead of HVM domains
>
>Hi,
>
>I was trying to find a solution for bug #521 ("video ram for hvm guests not
>properly accounted for when ballooning"). The trivial (although ugly) answer
>is to allocate an extra (hard-coded) 1026 pages in the getDomainMemory()
>function to account for the increase_reservation that qemu-dm will do.
>
>However, ugly or not, this doesn't work. In reality, an HVM domain requires
>some extra memory in addition to its nominal memory size. Here are some
>measurements I did (everything in MB; overhead is approximate and measured by
>looking at memory remaining in Xen's DMA and DOM memory zones before and after
>creating the HVM domU):
>
>Nominal Overhead
>------- --------
> 16 14.2
> 128 16.3
> 256 16.6
> 512 17.1
> 1024 18.4
>
>4 MB of this is due to the VM's video memory. I expect additional state would
>be stored in the qemu-dm process, but that would consume already-allocated dom0
>memory, and so wouldn't be represented above. I also see references to VMCBs
>/ VMCSs, but those are getting allocated on Xen's heap, and so also not
>represented above.
>
>So several questions:
>
>1. Where's the extra memory going?
>
>2. Should we even try to calculate it for auto-ballooning? It seems like many
>factors could affect it, and any such calculation would be very brittle.
>
>I'll gladly code up and test a patch to auto-balloon for HVM domains, but I
>first
>want to understand what's going on.
>
>Thanks,
>Chuck
>
>
>
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>Xen-devel@xxxxxxxxxxxxxxxxxxx
>http://lists.xensource.com/xen-devel
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