BSD11 vs BSD12 KVM performance

Bapat, Udayan Udayan.Bapat at
Sun May 5 13:29:20 UTC 2019

Thanks for the responses.

My bad. I meant BSD10 vs BSD11 and not 11 vs 12.

Also I am not doing any migration. This is purely a normal runtime behavior difference. We have enabled all the host hypervisor VM-x best practices. So could you please clarify what you mean by “intercepts always enabled”?

From: Anish <akgupt3 at>
Date: Saturday, May 4, 2019 at 8:54 PM
Cc: "Bapat, Udayan" <Udayan.Bapat at>, "freebsd-virtualization at" <freebsd-virtualization at>
Subject: Re: BSD11 vs BSD12 KVM performance

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Hi Udayan,

Intel VM-x and AMD SVM allow hypervisor to intercept TSC access for save/restore of VM migration, so when these intercepts are enabled, rdtsc will require switch between root and non-root mode which is expensive and may cost few hundreds of cpu cycles. Is it possible that one has these intercepts always enabled even when migration is not started?


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