RHEVM: Sockets Vs. Cores
Hello
Whats a better VM vCPU configuration in terms of overall performance and IO ?
1x Socket with 4 Cores
2x Sockets each with 2 Cores
4x Sockets each with 1 Core
Cheers
Responses
Hi Richard,
I like to hear from Red Hat about this, but I think the overall performance is the same.
I think cores and sockets are a feature to run your virtualized OS more efficiently with the licence it came with (example: software limited by cpu/sockets, but not by cores (multi core support) can run more effenciently on your hypervisor with the same licence).
-- Vincent
Vincent got it about right. To the host, every virtual core is a process thread to be executed, so the cores/sockets no matter how you split them up, end up as the same threads.
The real reason for having this separation is for the virtualization platform to present different CPU topologies to the VM, usually for the sake of easier licensing, when the guest OSs' license depends on a socket count, for example.
I have heard some reports of windows VMs running better on single core sockets, but I couldn't find real proof. So if you're facing a choice there, try different settings, and let us know if you've seen a difference. On the host level, for KVM, there is none, but the guests might behave slightly differently with different socket/core settings.
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