From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux ACPI <linux-acpi@vger.kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ACPI: processor: Add QoS requests for all CPUs
Date: Fri, 25 Oct 2019 14:21:32 +0530 [thread overview]
Message-ID: <20191025085132.qk6iynyavgvp7wlm@vireshk-i7> (raw)
In-Reply-To: <CAJZ5v0hyAX6zpr+2EzURg7ACmaXhbTAc7mBnr9ep11LkF1EBOg@mail.gmail.com>
On 25-10-19, 10:17, Rafael J. Wysocki wrote:
> On Fri, Oct 25, 2019 at 4:53 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> >
> > On 25-10-19, 02:41, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > >
> > > The _PPC change notifications from the platform firmware are per-CPU,
> > > so acpi_processor_ppc_init() needs to add a frequency QoS request
> > > for each CPU covered by a cpufreq policy to take all of them into
> > > account.
> > >
> > > Even though ACPI thermal control of CPUs sets frequency limits
> > > per processor package, it also needs a frequency QoS request for each
> > > CPU in a cpufreq policy in case some of them are taken offline and
> > > the frequency limit needs to be set through the remaining online
> > > ones (this is slightly excessive, because all CPUs covered by one
> > > cpufreq policy will set the same frequency limit through their QoS
> > > requests, but it is not incorrect).
> > >
> > > Modify the code in accordance with the above observations.
> >
> > I am not sure if I understood everything you just said, but I don't
> > see how things can break with the current code we have.
> >
> > Both acpi_thermal_cpufreq_init() and acpi_processor_ppc_init() are
> > called from acpi_processor_notifier() which is registered as a policy
> > notifier and is called when a policy is created or removed. Even if
> > some CPUs of a policy go offline, it won't matter as the request for
> > the policy stays and it will be dropped only when all the CPUs of a
> > policy go offline.
> >
> > What am I missing ?
>
> The way the request is used.
Yes, I missed the point :)
--
viresh
next prev parent reply other threads:[~2019-10-25 8:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 0:41 [PATCH] ACPI: processor: Add QoS requests for all CPUs Rafael J. Wysocki
2019-10-25 2:53 ` Viresh Kumar
2019-10-25 8:17 ` Rafael J. Wysocki
2019-10-25 8:46 ` Rafael J. Wysocki
2019-10-25 8:51 ` Viresh Kumar [this message]
2019-10-25 8:51 ` Viresh Kumar
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