Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <1565329531-12327-1-git-send-email-wanpengli@tencent.com> <fad8ceed-8b98-8fc4-5b6a-63bbca4059a8@redhat.com>
In-Reply-To: <fad8ceed-8b98-8fc4-5b6a-63bbca4059a8@redhat.com>
From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Mon, 12 Aug 2019 17:06:15 +0800
Message-ID: <CANRm+CwMMUEyZXmiUu5Y8GA=BEUYGLw31CRyZTc2uA+ct4Bamg@mail.gmail.com>
Subject: Re: [PATCH] KVM: LAPIC: Periodically revaluate appropriate lapic_timer_advance_ns
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 9 Aug 2019 at 18:24, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 09/08/19 07:45, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > Even if for realtime CPUs, cache line bounces, frequency scaling, presence
> > of higher-priority RT tasks, etc can cause different response. These
> > interferences should be considered and periodically revaluate whether
> > or not the lapic_timer_advance_ns value is the best, do nothing if it is,
> > otherwise recaluate again.
>
> How much fluctuation do you observe between different runs?

Sometimes can ~1000 cycles after converting to guest tsc freq.

Regards,
Wanpeng Li