linux-kernel - Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency requests

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Message-ID: <20180509070113.GB52784@joelaf.mtv.corp.google.com>
Date:   Wed, 9 May 2018 00:01:13 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Juri Lelli <juri.lelli@...hat.com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        linux-kernel@...r.kernel.org,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Joel Fernandes <joelaf@...gle.com>, linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH] sched/cpufreq/schedutil: handling urgent frequency
 requests

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..

- Joel