Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 5/31/22 16:52, Durrant, Paul wrote: >>> -----Original Message----- >>> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> >>> Sent: 31 May 2022 15:44 >>> To: Allister, Jack <jalliste@xxxxxxxxxx> >>> Cc: bp@xxxxxxxxx; diapop@xxxxxxxxxxxx; hpa@xxxxxxxxx; jmattson@xxxxxxxxxx; joro@xxxxxxxxxx; >>> kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; metikaya@xxxxxxxxxxxx; mingo@xxxxxxxxxx; >>> pbonzini@xxxxxxxxxx; rkrcmar@xxxxxxxxxx; sean.j.christopherson@xxxxxxxxx; tglx@xxxxxxxxxxxxx; >>> vkuznets@xxxxxxxxxx; wanpengli@xxxxxxxxxxx; x86@xxxxxxxxxx >>> 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
