linux-kernel - Re: [PATCH v7 1/2] cpufreq: schedutil: Make iowait boost more energy efficient

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Date:   Mon, 24 Jul 2017 14:27:45 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Joel Fernandes <joelaf@...gle.com>
Cc:     linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Andres Oportus <andresoportus@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        linux-pm@...r.kernel.org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v7 1/2] cpufreq: schedutil: Make iowait boost more energy
 efficient

On 23-07-17, 08:54, Joel Fernandes wrote:
> Currently the iowait_boost feature in schedutil makes the frequency go to max
> on iowait wakeups.  This feature was added to handle a case that Peter
> described where the throughput of operations involving continuous I/O requests
> [1] is reduced due to running at a lower frequency, however the lower
> throughput itself causes utilization to be low and hence causing frequency to
> be low hence its "stuck".
> 
> Instead of going to max, its also possible to achieve the same effect by
> ramping up to max if there are repeated in_iowait wakeups happening. This patch
> is an attempt to do that. We start from a lower frequency (policy->min)
> and double the boost for every consecutive iowait update until we reach the
> maximum iowait boost frequency (iowait_boost_max).
> 
> I ran a synthetic test (continuous O_DIRECT writes in a loop) on an x86 machine
> with intel_pstate in passive mode using schedutil. In this test the iowait_boost
> value ramped from 800MHz to 4GHz in 60ms. The patch achieves the desired improved
> throughput as the existing behavior.
> 
> [1] https://patchwork.kernel.org/patch/9735885/
> 
> Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: Len Brown <lenb@...nel.org>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Suggested-by: Viresh Kumar <viresh.kumar@...aro.org>
> Signed-off-by: Joel Fernandes <joelaf@...gle.com>
> ---
>  kernel/sched/cpufreq_schedutil.c | 38 ++++++++++++++++++++++++++++++++------
>  1 file changed, 32 insertions(+), 6 deletions(-)

You Send V7 [1-2]/2 twice, Are they different ?

For both the patches:

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh