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Re: [Qemu-discuss] Why do additional cores reduce performance?
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-discuss] Why do additional cores reduce performance? |
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Date: |
Tue, 16 Dec 2014 17:31:13 +0100 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 |
On 16/12/2014 17:22, Oleg Ovechko wrote:
>> What is your benchmark?
>
> I've tried different ways (CrystalDiskMark 3.0.3 x64, ATTO Disk
> Banchmark v2.47) all give same result.
All are run on the AHCI passthrough disk(s), right?
> When everything is enabled in BIOS it is 6:23 on real Windows versus
> 9:03 on virtualized...
>
> Phil Ehrens has sent me link
> https://lists.gnu.org/archive/html/qemu-discuss/2014-10/msg00036.html
> If I don't misunderstand, it means kvm/qemu simply is not designed for
> multi-threading.
No, it means TCG does not support multithreading. KVM does, and you are
using it.
> I guess I need to try different hypervisor. 50% performance is too
> high price especially when VT-x and VT-d are meant to make it 0%
It is surprising to me too.
Paolo