linux-kernel - Re: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available

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Message-ID: <20190828143916.GA13725@amt.cnet>
Date:   Wed, 28 Aug 2019 11:39:18 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Wanpeng Li <kernellwp@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when
 dedicated physical CPUs are available

On Wed, Aug 28, 2019 at 10:45:44AM +0200, Rafael J. Wysocki wrote:
> On Wed, Aug 28, 2019 at 10:34 AM Wanpeng Li <kernellwp@...il.com> wrote:
> >
> > On Tue, 27 Aug 2019 at 08:43, Wanpeng Li <kernellwp@...il.com> wrote:
> > >
> > > Cc Michael S. Tsirkin,
> > > On Tue, 27 Aug 2019 at 04:42, Marcelo Tosatti <mtosatti@...hat.com> wrote:
> > > >
> > > > On Tue, Aug 13, 2019 at 08:55:29AM +0800, Wanpeng Li wrote:
> > > > > On Sun, 4 Aug 2019 at 04:21, Marcelo Tosatti <mtosatti@...hat.com> wrote:
> > > > > >
> > > > > > On Thu, Aug 01, 2019 at 06:54:49PM +0200, Paolo Bonzini wrote:
> > > > > > > On 01/08/19 18:51, Rafael J. Wysocki wrote:
> > > > > > > > On 8/1/2019 9:06 AM, Wanpeng Li wrote:
> > > > > > > >> From: Wanpeng Li <wanpengli@...cent.com>
> > > > > > > >>
> > > > > > > >> The downside of guest side polling is that polling is performed even
> > > > > > > >> with other runnable tasks in the host. However, even if poll in kvm
> > > > > > > >> can aware whether or not other runnable tasks in the same pCPU, it
> > > > > > > >> can still incur extra overhead in over-subscribe scenario. Now we can
> > > > > > > >> just enable guest polling when dedicated pCPUs are available.
> > > > > > > >>
> > > > > > > >> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > > > >> Cc: Paolo Bonzini <pbonzini@...hat.com>
> > > > > > > >> Cc: Radim Krčmář <rkrcmar@...hat.com>
> > > > > > > >> Cc: Marcelo Tosatti <mtosatti@...hat.com>
> > > > > > > >> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> > > > > > > >
> > > > > > > > Paolo, Marcelo, any comments?
> > > > > > >
> > > > > > > Yes, it's a good idea.
> > > > > > >
> > > > > > > Acked-by: Paolo Bonzini <pbonzini@...hat.com>
> >
> > Hi Marcelo,
> >
> > If you don't have more concern, I guess Rafael can apply this patch
> > now since the merge window is not too far.
> 
> I will likely queue it up later today and it will go to linux-next
> early next week.
> 
> Thanks!

NACK patch.

Just don't load the haltpoll driver.