Date: Sat, 4 May 2019 17:54:39 -0700 From: Anish <akgupt3@gmail.com> Cc: "Bapat, Udayan" <Udayan.Bapat@netapp.com>, "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org> Subject: Re: BSD11 vs BSD12 KVM performance Message-ID: <CALnRwMSAje_SWxWPk%2BaHcJH3gjXaWoQbjHnUMkKkLdZjiAyPBA@mail.gmail.com> In-Reply-To: <b83b1234-6359-2b26-d9ce-9eb261861eda@omnilan.de> References: <D2BA45B3-5156-424F-A74A-C41FE0E20CEC@netapp.com> <b83b1234-6359-2b26-d9ce-9eb261861eda@omnilan.de>
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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? -Anish
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