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Re: [Qemu-devel] QEMU -smp paramater: Will multiplue threads and cores i
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [Qemu-devel] QEMU -smp paramater: Will multiplue threads and cores improve performance? |
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Date: |
Wed, 21 Dec 2016 11:23:42 +0000 |
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User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Wed, Dec 21, 2016 at 04:44:08PM +0800, Bob Chen wrote:
> -smp 16
>
> -smp cores=4,threads=4,sockets=1
>
>
> Which one has better performance? The scenario is guest VMs running on
> cloud server.
It's more complicated than that.
The CPU topology (cores, threads, sockets) can be used by guest kernels
to make scheduling decisions.
If you pin vcpu threads to host cpus and configure the guest with
an accurate CPU topology then you can expect the guest kernel to make
the best decisions.
If you do not pin vcpu threads then you cannot expect any consistent
performance advantage by specifying the CPU topology.
Stefan
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