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Date: Wed, 9 May 2018 10:23:50 +0200
From: Juri Lelli <juri.lelli@redhat.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: 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>
Subject: Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency
 requests
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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.