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[Xen-devel] Re: [Xen-users] Does vt-x itself have perf. impact on Hyperv

To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, "Xen devel list" <xen-devel@xxxxxxxxxxxxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Xen-users] Does vt-x itself have perf. impact on Hypervisor w/o considering HVM?
From: "Liang Yang" <multisyncfe991@xxxxxxxxxxx>
Date: Tue, 23 Jan 2007 09:15:02 -0700
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Without VT-x support, binary translation has to be used to make those non-virtualizable instructions throw exception. With VT-x support, no binary translation is needed. So you mean, binary translation could be implemented as efficient as they are done in hardware?

Thanks,

Liang

----- Original Message ----- From: "Petersson, Mats" <Mats.Petersson@xxxxxxx> To: "Liang Yang" <multisyncfe991@xxxxxxxxxxx>; "Xen devel list" <xen-devel@xxxxxxxxxxxxxxxxxxx>; <xen-users@xxxxxxxxxxxxxxxxxxx>
Sent: Tuesday, January 23, 2007 3:05 AM
Subject: RE: [Xen-users] Does vt-x itself have perf. impact on Hypervisor w/o considering HVM?


-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Liang Yang
Sent: 22 January 2007 18:33
To: Xen devel list; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-users] Does vt-x itself have perf. impact on
Hypervisor w/o considering HVM?

Hello,

Suppose I have two different kinds of CPUs which have exactly
the same
configuration except one supports VT-X while the other does
not. If I want
to test the I/O performance (or other perf. testing which is not
particularly related to I/O) of the both domain0 and
Para-Virtualized Guest
Domain (HVM domain is not considered), shall I expect to get the same
performance results on these two CPUs?

Assuming ALL other aspects are the same, when you're not using HVM,
there should be absolutely zero impact from it (aside from it using up a
few kilobytes of memory, to be precise, HVM (including both VMX and SVM)
takes up 129459 bytes when not used - more memory is allocated
dynamically when it's being used for obvious reasons. For modern
systems, that's so small that it doesn't matter).

--
Mats

Thanks,

Liang


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