Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: ...\n | Date | Wed, 01 Jun 2022 09:57:14 +0200 |
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Paolo Bonzini <pbonzini@redhat.com> writes:
> On 5/31/22 16:52, Durrant, Paul wrote: >>> -----Original Message----- >>> From: Peter Zijlstra <peterz@infradead.org> >>> Sent: 31 May 2022 15:44 >>> To: Allister, Jack <jalliste@amazon.com> >>> Cc: bp@alien8.de; diapop@amazon.co.uk; hpa@zytor.com; jmattson@google.com; joro@8bytes.org; >>> kvm@vger.kernel.org; linux-kernel@vger.kernel.org; metikaya@amazon.co.uk; mingo@redhat.com; >>> pbonzini@redhat.com; rkrcmar@redhat.com; sean.j.christopherson@intel.com; tglx@linutronix.de; >>> vkuznets@redhat.com; wanpengli@tencent.com; x86@kernel.org >>> Subject: RE: [EXTERNAL]...\n >>> >>> >>> On Tue, May 31, 2022 at 02:02:36PM +0000, Jack Allister wrote: >>>> The reasoning behind this is that you may want to run a guest at a >>>> lower CPU frequency for the purposes of trying to match performance >>>> parity between a host of an older CPU type to a newer faster one. >>> >>> That's quite ludicrus. Also, then it should be the host enforcing the >>> cpufreq, not the guest. >> >> I'll bite... What's ludicrous about wanting to run a guest at a lower CPU freq to minimize observable change in whatever workload it is running? > > Well, the right API is cpufreq, there's no need to make it a KVM > functionality.
KVM may probably use the cpufreq API to run each vCPU at the desired frequency: I don't quite see how this can be done with a VMM today when it's not a 1-vCPU-per-1-pCPU setup.
-- Vitaly
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