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
In-Reply-To: <20180509082350.GB1681@localhost.localdomain>
References: <1525704215-8683-1-git-send-email-claudio@evidence.eu.com>
 <20180508065435.bcht6dyb3rpp6gk5@vireshk-i7> <20180509045425.GA158882@joelaf.mtv.corp.google.com>
 <20180509064530.GA1681@localhost.localdomain> <20180509065449.c5zotxqmuyatjgfd@vireshk-i7>
 <20180509070113.GB52784@joelaf.mtv.corp.google.com> <CAJZ5v0hNgvd=0dKstXRsbHhtrc6m+ugS5kjPOq2B8k55ioX0MA@mail.gmail.com>
 <20180509082350.GB1681@localhost.localdomain>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 9 May 2018 10:25:19 +0200
Message-ID: <CAJZ5v0hkeCOybZo4LPpwiE0PG8msCWQkgiHJbpi-6zJHtOQbfg@mail.gmail.com>
Subject: Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency requests
To:     Juri Lelli <juri.lelli@redhat.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Claudio Scordino <claudio@evidence.eu.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>,
        Luca Abeni <luca.abeni@santannapisa.it>,
        Joel Fernandes <joelaf@google.com>,
        Linux PM <linux-pm@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, May 9, 2018 at 10:23 AM, Juri Lelli <juri.lelli@redhat.com> wrote:
> On 09/05/18 10:05, Rafael J. Wysocki wrote:
>> On Wed, May 9, 2018 at 9:01 AM, Joel Fernandes <joel@joelfernandes.org> wrote:
>> > On Wed, May 09, 2018 at 12:24:49PM +0530, Viresh Kumar wrote:
>> >> On 09-05-18, 08:45, Juri Lelli wrote:
>> >> > On 08/05/18 21:54, Joel Fernandes wrote:
>> >> > Isn't this potentially introducing unneeded irq pressure (and doing the
>> >> > whole wakeup the kthread thing), while the already active kthread could
>> >> > simply handle multiple back-to-back requests before going to sleep?
>> >>
>> >> And then we may need more instances of the work item and need to store
>> >> a different value of next_freq with each work item, as we can't use
>> >> the common one anymore as there would be races around accessing it ?
>> >
>> > Exactly. I think it also doesn't make sense to over write an already
>> > committed request either so better to store them separate (?). After the
>> > "commit", that previous request is done..
>>
>> Why is it?
>>
>> In the non-fast-switch case the "commit" only means queuing up an
>> irq_work.  Which BTW is one of the reasons for having work_in_progress
>> even if your kthread can handle multiple work items in one go.
>>
>> You may try to clear work_in_progress in sugov_irq_work() instead of
>> in sugov_work(), though.
>>
>> BTW, I'm not sure if the comment in sugov_irq_work() still applies.  Juri?
>
> It doesn't anymore. sugov kthreads are now being "ignored". Should have
> remove it with the DL set of changes, sorry about that.

No worries, you can still do that. ;-)