linux-kernel - Re: [PATCH] sched: introduce configurable delay before entering idle

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Message-ID: <CANRm+CwFyqCeHKOv-M134k4mvpjqnaO-pUO_p0W0QTPL36+ibA@mail.gmail.com>
Date:   Wed, 15 May 2019 09:45:14 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     "Raslan, KarimAllah" <karahmed@...zon.de>
Cc:     "mtosatti@...hat.com" <mtosatti@...hat.com>,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "bsd@...hat.com" <bsd@...hat.com>,
        "aarcange@...hat.com" <aarcange@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "ankur.a.arora@...cle.com" <ankur.a.arora@...cle.com>
Subject: Re: [PATCH] sched: introduce configurable delay before entering idle

On Mon, 13 May 2019 at 19:52, Raslan, KarimAllah <karahmed@...zon.de> wrote:
>
> On Mon, 2019-05-13 at 07:31 -0400, Konrad Rzeszutek Wilk wrote:
> > On May 13, 2019 5:20:37 AM EDT, Wanpeng Li <kernellwp@...il.com> wrote:
> > >
> > > On Wed, 8 May 2019 at 02:57, Marcelo Tosatti <mtosatti@...hat.com>
> > > wrote:
> > > >
> > > >
> > > >
> > > > Certain workloads perform poorly on KVM compared to baremetal
> > > > due to baremetal's ability to perform mwait on NEED_RESCHED
> > > > bit of task flags (therefore skipping the IPI).
> > >
> > > KVM supports expose mwait to the guest, if it can solve this?
> > >
> >
> >
> > There is a bit of problem with that. The host will see 100% CPU utilization even if the guest is idle and taking long naps..
> >
> > Which depending on your dashboard can look like the machine is on fire.
>
> This can also be fixed. I have a patch that kind of expose proper information
> about the *real* utilization here if that would be help.

You can have a post.

Regards,
Wanpeng Li