From: Viresh Kumar <viresh.kumar@linaro.org>
To: Steve Muckle <steve.muckle@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
"Rafael J . Wysocki" <rjw@rjwysocki.net>,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Juri Lelli <Juri.Lelli@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Steve Muckle <smuckle@linaro.org>
Subject: Re: [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil
Date: Thu, 21 Jul 2016 13:01:12 -0700 [thread overview]
Message-ID: <20160721200112.GG3122@ubuntu> (raw)
In-Reply-To: <1468441527-23534-1-git-send-email-smuckle@linaro.org>
On 13-07-16, 13:25, Steve Muckle wrote:
> Invoking the cpufreq driver to set a frequency can be expensive. On platforms
> with a cpufreq driver that does not support fast switching a thread must be
> woken to complete the operation. IPIs will also occur if and when support to
> process remote task wakeups is added in schedutil.
>
> Currently schedutil calculates a raw frequency request from scheduler
> utilization data. This raw frequency request does not correlate to supported
> cpufreq driver frequencies aside from being capped by the CPU's maximum
> frequency. Consequently, there may be many consecutive requests for different
> raw frequency values which all translate to the same driver-supported
> frequency. For example on a platform with 3 supported frequencies 200MHz,
> 400MHz, and 600MHz, raw requests for 257MHz, 389MHz, and 307MHz all map to a
> driver-supported frequency of 400MHz in schedutil. Assuming these requests were
> consecutive and there were no changes in policy limits (min/max), there is no
> need to issue the second or third request.
>
> In order to resolve a raw frequency request to a driver-supported one a new
> cpufreq API is added, cpufreq_driver_resolve_freq(). This API relies on a new
> cpufreq driver callback in the case of ->target() style drivers. Otherwise it
> uses the existing frequency table operations.
>
> Lookups are cached both in cpufreq_driver_resolve_freq() (for the benefit of the
> driver) and in schedutil.
>
> Changes since v2:
> - incorporated feedback from Viresh to use resolve_freq driver callbacks
> only for ->target() style drivers, to use cpufreq's freq table operations,
> and move freq mapping caching into cpufreq policy
Sorry for the delay buddy :(
I have some concerns for the first patch. The second and third patch
look fine. Feel free to add my
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
for them.
--
viresh
prev parent reply other threads:[~2016-07-21 20:01 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-13 20:25 [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Steve Muckle
2016-07-13 20:25 ` [PATCH v3 1/3] cpufreq: add cpufreq_driver_resolve_freq() Steve Muckle
2016-07-21 19:59 ` Viresh Kumar
2016-07-21 20:31 ` Rafael J. Wysocki
2016-07-21 20:30 ` Viresh Kumar
2016-07-21 20:52 ` Rafael J. Wysocki
2016-07-21 20:52 ` Viresh Kumar
2016-07-21 21:19 ` Rafael J. Wysocki
2016-07-21 21:16 ` Viresh Kumar
2016-07-21 23:21 ` Steve Muckle
2016-07-21 23:29 ` Steve Muckle
2016-07-21 23:31 ` Viresh Kumar
2016-07-21 23:30 ` Viresh Kumar
2016-07-21 23:36 ` Steve Muckle
2016-07-21 23:41 ` Steve Muckle
2016-07-22 0:44 ` Steve Muckle
2016-07-22 15:16 ` Viresh Kumar
2016-07-22 17:49 ` Steve Muckle
2016-07-21 21:13 ` Viresh Kumar
2016-07-13 20:25 ` [PATCH v3 2/3] cpufreq: schedutil: map raw required frequency to driver frequency Steve Muckle
2016-07-13 20:25 ` [PATCH v3 3/3] cpufreq: acpi-cpufreq: use cached frequency mapping when possible Steve Muckle
2016-07-14 10:02 ` [PATCH v3 0/3] cpufreq: avoid redundant driver calls in schedutil Pingbo Wen
2016-07-14 18:00 ` Steve Muckle
2016-07-21 20:01 ` Viresh Kumar [this message]
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