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From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Tue, 9 Jul 2019 10:06:09 +0800
Message-ID: <CANRm+CyCwz7V3fvx48FXiSXkDer1B6bMGwzvoA9vgccxK6gqZw@mail.gmail.com>
Subject: Re: cputime takes cstate into consideration
To:     Ankur Arora <ankur.a.arora@oracle.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        "Raslan, KarimAllah" <karahmed@amazon.de>,
        "boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
        "joao.m.martins@oracle.com" <joao.m.martins@oracle.com>,
        "konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "rkrcmar@redhat.com" <rkrcmar@redhat.com>,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "mtosatti@redhat.com" <mtosatti@redhat.com>,
        Frederic Weisbecker <frederic@kernel.org>
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also Cc Frederic,
On Tue, 9 Jul 2019 at 10:00, Ankur Arora <ankur.a.arora@oracle.com> wrote:
>
> On 2019-06-26 12:23 p.m., Thomas Gleixner wrote:
> > On Wed, 26 Jun 2019, Raslan, KarimAllah wrote:
> >> On Wed, 2019-06-26 at 10:54 -0400, Konrad Rzeszutek Wilk wrote:
> >>> There were some ideas that Ankur (CC-ed) mentioned to me of using the perf
> >>> counters (in the host) to sample the guest and construct a better
> >>> accounting idea of what the guest does. That way the dashboard
> >>> from the host would not show 100% CPU utilization.
> >>
> >> You can either use the UNHALTED cycles perf-counter or you can use MPERF/APERF
> >> MSRs for that. (sorry I got distracted and forgot to send the patch)
> >
> > Sure, but then you conflict with the other people who fight tooth and nail
> > over every single performance counter.
> How about using Intel PT PwrEvt extensions? This should allow us to
> precisely track idle residency via just MWAIT and TSC packets. Should
> be pretty cheap too. It's post Cascade Lake though.
>
> Ankur
>
> >
> > Thanks,
> >
> >       tglx
> >
>