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;
Date:   Thu, 29 Aug 2019 09:53:04 -0300
From:   Marcelo Tosatti <mtosatti@redhat.com>
To:     Wanpeng Li <kernellwp@gmail.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when
 dedicated physical CPUs are available
Message-ID: <20190829125304.GA12214@amt.cnet>
References: <20190803202058.GA9316@amt.cnet>
 <CANRm+CwtHBOVWFcn+6Z3Ds7dEcNL2JP+b6hLRS=oeUW98A24MQ@mail.gmail.com>
 <20190826204045.GA24697@amt.cnet>
 <CANRm+Cx0+V67Ek7FhSs61ZqZL3MgV88Wdy17Q6UA369RH7=dgQ@mail.gmail.com>
 <CANRm+CxqYMzgvxYyhZLmEzYd6SLTyHdRzKVaSiHO-4SV+OwZUQ@mail.gmail.com>
 <CAJZ5v0iQc0-WzqeyAh-6m5O-BLraRMj+Z7sqvRgGwh2u2Hp7cg@mail.gmail.com>
 <20190828143916.GA13725@amt.cnet>
 <CAJZ5v0jiBprGrwLAhmLbZKpKUvmKwG9w4_R7+dQVqswptis5Qg@mail.gmail.com>
 <20190829120422.GC4949@amt.cnet>
 <CANRm+CwYq7NZeKffioWcHy_oWGyeHqXsygF_cppMD17mHuVgYw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CANRm+CwYq7NZeKffioWcHy_oWGyeHqXsygF_cppMD17mHuVgYw@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Aug 29, 2019 at 08:16:41PM +0800, Wanpeng Li wrote:
> > Current situation regarding haltpoll driver is:
> >
> > overcommit group: haltpoll driver is not loaded by default, they are
> > happy.
> >
> > non overcommit group: boots without "realtime hints" flag, loads haltpoll driver,
> > happy.
> >
> > Situation with patch above:
> >
> > overcommit group: haltpoll driver is not loaded by default, they are
> > happy.
> >
> > non overcommit group: boots without "realtime hints" flag, haltpoll driver
> > cannot be loaded.
> 
> non overcommit group, if they don't care latency/performance, they
> don't need to enable haltpoll, "realtime hints" etc. Otherwise, they
> should better tune.

As mentioned before, "being overcommitted" is a property which is transitional.

A static true/false scheme reflects this poorly.

Therefore the OS should detect it and act accordingly.