From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
"Durrant, Paul" <pdurrant@amazon.co.uk>
Cc: "Allister, Jack" <jalliste@amazon.com>,
"bp@alien8.de" <bp@alien8.de>,
"diapop@amazon.co.uk" <diapop@amazon.co.uk>,
"hpa@zytor.com" <hpa@zytor.com>,
"jmattson@google.com" <jmattson@google.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"metikaya@amazon.co.uk" <metikaya@amazon.co.uk>,
"mingo@redhat.com" <mingo@redhat.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>,
"sean.j.christopherson@intel.com"
<sean.j.christopherson@intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"wanpengli@tencent.com" <wanpengli@tencent.com>,
"x86@kernel.org" <x86@kernel.org>
Subject: Re: ...\n
Date: Wed, 01 Jun 2022 10:03:06 +0200 [thread overview]
Message-ID: <87r148olol.fsf@redhat.com> (raw)
In-Reply-To: <YpcMw2TgNWzrcoRm@worktop.programming.kicks-ass.net>
Peter Zijlstra <peterz@infradead.org> writes:
> On Tue, May 31, 2022 at 02:52:04PM +0000, Durrant, Paul wrote:
...
>>
>> 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?
>
> *why* would you want to do that? Everybody wants their stuff done
> faster.
>
FWIW, I can see a valid use-case: imagine you're running some software
which calibrates itself in the beginning to run at some desired real
time speed but then the VM running it has to be migrated to a host with
faster (newer) CPUs. I don't have a real world examples out of top of my
head but I remember some old DOS era games were impossible to play on
newer CPUs because everything was happenning too fast. Maybe that's the
case :-)
--
Vitaly
next prev parent reply other threads:[~2022-06-01 8:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-31 10:59 [PATCH] KVM: VMX: CPU frequency scaling for intel x86_64 KVM guests Jack Allister
2022-05-31 11:43 ` Metin Kaya
2022-05-31 18:11 ` Paolo Bonzini
2022-06-01 12:55 ` David Woodhouse
2022-05-31 13:38 ` Peter Zijlstra
2022-05-31 14:02 ` ...\n Jack Allister
2022-05-31 14:44 ` ...\n Peter Zijlstra
2022-05-31 14:52 ` ...\n Durrant, Paul
2022-05-31 15:51 ` ...\n Paolo Bonzini
2022-06-01 7:57 ` ...\n Vitaly Kuznetsov
2022-06-01 8:59 ` ...\n Paolo Bonzini
2022-06-01 10:19 ` ...\n Peter Zijlstra
2022-06-01 6:52 ` ...\n Peter Zijlstra
2022-06-01 8:03 ` Vitaly Kuznetsov [this message]
2022-06-01 8:25 ` ...\n Christophe de Dinechin
2022-06-01 8:54 ` ...\n Durrant, Paul
2022-06-01 8:57 ` ...\n Paolo Bonzini
2022-06-01 9:20 ` ...\n Durrant, Paul
2022-06-01 9:43 ` ...\n Amit Shah
2022-06-01 13:14 ` ...\n David Woodhouse
2022-05-31 14:52 ` ...\n Paolo Bonzini
2022-05-31 15:27 ` ...\n Peter Zijlstra
2022-05-31 15:01 ` [PATCH] KVM: VMX: CPU frequency scaling for intel x86_64 KVM guests Vitaly Kuznetsov
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