From: Saravana Kannan <skannan@codeaurora.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
Rafael Wysocki <rjw@rjwysocki.net>,
Ingo Molnar <mingo@redhat.com>,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
smuckle.linux@gmail.com, eas-dev@lists.linaro.org
Subject: Re: [Eas-dev] [PATCH V3 2/3] cpufreq: schedutil: Process remote callback for shared policies
Date: Wed, 26 Jul 2017 13:56:10 -0700 [thread overview]
Message-ID: <597901EA.6080702@codeaurora.org> (raw)
In-Reply-To: <20170720122239.licc6yjd7jwipcvk@hirez.programming.kicks-ass.net>
On 07/20/2017 05:22 AM, Peter Zijlstra wrote:
> So the typical implementation of fast switching we're thinking of is the
> CPU writing the DVFS request into a machine register. Now machine
> registers are typically per logical CPU.
Writing to a memory addressable register. AFAIK, ARM has no support for
a machine register for DVFS request. So, even if any ARM licensee wants
to add one, it won't be possible.
Also, even if we have an ARM CPU with a machine register, rejecting a
valid frequency switch just because it happened to come on a different
CPU seem silly (you can have a huge performance hit due to that). A much
better solution is to just make an IPI to the right CPU and execute the
machine register write on the right CPU.
-Saravana
--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
next prev parent reply other threads:[~2017-07-26 20:56 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-13 6:44 [PATCH V3 0/3] sched: cpufreq: Allow remote callbacks Viresh Kumar
2017-07-13 6:44 ` [PATCH V3 1/3] sched: cpufreq: Allow remote cpufreq callbacks Viresh Kumar
2017-07-21 13:03 ` Peter Zijlstra
2017-07-24 11:01 ` Viresh Kumar
2017-07-24 13:47 ` Peter Zijlstra
2017-07-26 6:29 ` Viresh Kumar
2017-07-26 8:12 ` Peter Zijlstra
2017-07-26 17:26 ` Rafael J. Wysocki
2017-07-26 21:00 ` [Eas-dev] " Saravana Kannan
2017-07-27 3:30 ` Viresh Kumar
2017-07-27 19:55 ` Saravana Kannan
2017-07-28 4:33 ` Joel Fernandes (Google)
2017-07-28 6:00 ` Viresh Kumar
2017-07-28 21:05 ` Saravana Kannan
2017-07-31 3:58 ` Viresh Kumar
2017-07-13 6:44 ` [PATCH V3 2/3] cpufreq: schedutil: Process remote callback for shared policies Viresh Kumar
2017-07-14 2:02 ` [Eas-dev] " Saravana Kannan
2017-07-14 5:03 ` Viresh Kumar
2017-07-20 13:58 ` Peter Zijlstra
2017-07-20 12:22 ` Peter Zijlstra
2017-07-20 15:11 ` Sudeep Holla
2017-07-26 20:56 ` Saravana Kannan [this message]
2017-07-13 6:44 ` [PATCH V3 3/3] cpufreq: governor: " Viresh Kumar
2017-07-13 15:17 ` [PATCH V3 0/3] sched: cpufreq: Allow remote callbacks Rafael J. Wysocki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=597901EA.6080702@codeaurora.org \
--to=skannan@codeaurora.org \
--cc=eas-dev@lists.linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rjw@rjwysocki.net \
--cc=smuckle.linux@gmail.com \
--cc=viresh.kumar@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.