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References: <20191027105243.34339-1-like.xu@linux.intel.com> <20191027105243.34339-6-like.xu@linux.intel.com>
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From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Thu, 14 Nov 2019 11:51:11 +0800
Message-ID: <CANRm+Cz3-k6Bct0JAN=m1emT5j4NgULjURyHz0vCDabq00nk4Q@mail.gmail.com>
Subject: Re: [PATCH v4 5/6] KVM: x86/vPMU: Reuse perf_event to avoid
 unnecessary pmc_reprogram_counter
To:     Like Xu <like.xu@linux.intel.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Jim Mattson <jmattson@google.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
        Jiri Olsa <jolsa@redhat.com>, Joerg Roedel <joro@8bytes.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>, kan.liang@intel.com,
        wei.w.wang@intel.com, LKML <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>
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On Mon, 28 Oct 2019 at 21:06, Like Xu <like.xu@linux.intel.com> wrote:
>
> The perf_event_create_kernel_counter() in the pmc_reprogram_counter() is
> a heavyweight and high-frequency operation, especially when host disables
> the watchdog (maximum 21000000 ns) which leads to an unacceptable latency

Why when host disables the watchdog,
perf_event_create_kernel_counter() is more heavyweight and
high-frequency operation?

    Wanpeng