From: Steve Muckle <steve.muckle@linaro.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Steve Muckle <steve.muckle@linaro.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"linux-pm@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>,
Michael Turquette <mturquette@baylibre.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Len Brown <lenb@kernel.org>
Subject: Re: [PATCH 4/5] cpufreq: schedutil: map raw required frequency to CPU-supported frequency
Date: Thu, 19 May 2016 12:35:47 -0700 [thread overview]
Message-ID: <20160519193547.GF17223@graphite.smuckle.net> (raw)
In-Reply-To: <CAJZ5v0iNc767ANwQpju4D9XMfjADuZrfvuQvQ_CBmcDKUAuEAA@mail.gmail.com>
On Thu, May 19, 2016 at 01:37:40AM +0200, Rafael J. Wysocki wrote:
> On Mon, May 9, 2016 at 11:20 PM, Steve Muckle <steve.muckle@linaro.org> wrote:
> > The mechanisms for remote CPU updates and slow-path frequency
> > transitions are relatively expensive - the former is an IPI while the
> > latter requires waking up a thread to do work. These activities should
> > be avoided if they are not necessary. To that end, calculate the
> > actual target-supported frequency required by the new utilization
> > value in schedutil. If it is the same as the previously requested
> > frequency then there is no need to continue with the update.
>
> Unless the max/min limits changed in the meantime, right?
Right, I'll amend the commit text. The functionality is correct AFAICS.
> >
> > Signed-off-by: Steve Muckle <smuckle@linaro.org>
> > ---
> > kernel/sched/cpufreq_schedutil.c | 14 +++++++++++++-
> > 1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 6cb2ecc204ec..e185075fcb5c 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -153,14 +153,26 @@ static void sugov_update_commit(struct sugov_cpu *sg_cpu, int cpu, u64 time,
> > * next_freq = C * curr_freq * util_raw / max
> > *
> > * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
> > + *
> > + * The lowest target-supported frequency which is equal or greater than the raw
> > + * next_freq (as calculated above) is returned, or the CPU's max_freq if such
> > + * a target-supported frequency does not exist.
> > */
> > static unsigned int get_next_freq(struct cpufreq_policy *policy,
> > unsigned long util, unsigned long max)
> > {
> > + struct cpufreq_frequency_table *entry;
> > unsigned int freq = arch_scale_freq_invariant() ?
> > policy->cpuinfo.max_freq : policy->cur;
> > + unsigned int target_freq = UINT_MAX;
> > +
> > + freq = (freq + (freq >> 2)) * util / max;
> > +
> > + cpufreq_for_each_valid_entry(entry, policy->freq_table)
> > + if (entry->frequency >= freq && entry->frequency < target_freq)
> > + target_freq = entry->frequency;
>
> Please don't assume that every driver will have a frequency table.
> That may not be the case in the future (and I'm not even sure about
> the existing CPPC driver for that matter).
For platforms without a frequency table I guess we can just continue
with the current behavior, passing in the raw calculated frequency. I'll
make this change.
At some point I imagine those platforms will want to somehow achieve
similar behavior to avoid very small transitions that do not result in
real benefit. Maybe some sort of threshold % in the schedutil down the
road.
thanks,
Steve
next prev parent reply other threads:[~2016-05-19 19:35 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 21:20 [PATCH 0/5] cpufreq: schedutil: improve latency of response Steve Muckle
2016-05-09 21:20 ` [PATCH 1/5] sched: cpufreq: add cpu to update_util_data Steve Muckle
2016-05-18 23:13 ` Rafael J. Wysocki
2016-05-09 21:20 ` [PATCH 2/5] cpufreq: schedutil: support scheduler cpufreq callbacks on remote CPUs Steve Muckle
2016-05-18 23:24 ` Rafael J. Wysocki
2016-05-19 18:40 ` Steve Muckle
2016-05-19 20:55 ` Rafael J. Wysocki
2016-05-19 22:59 ` Steve Muckle
2016-05-19 23:14 ` Rafael J. Wysocki
2016-05-09 21:20 ` [PATCH 3/5] sched: cpufreq: call cpufreq hook from " Steve Muckle
2016-05-18 23:33 ` Rafael J. Wysocki
2016-05-19 12:00 ` Rafael J. Wysocki
2016-05-19 19:19 ` Steve Muckle
2016-05-19 21:06 ` Rafael J. Wysocki
2016-05-19 23:04 ` Steve Muckle
2016-05-21 19:46 ` Steve Muckle
2016-06-01 20:09 ` Steve Muckle
2016-05-09 21:20 ` [PATCH 4/5] cpufreq: schedutil: map raw required frequency to CPU-supported frequency Steve Muckle
2016-05-18 23:37 ` Rafael J. Wysocki
2016-05-19 19:35 ` Steve Muckle [this message]
2016-05-19 21:07 ` Rafael J. Wysocki
2016-05-09 21:20 ` [PATCH 5/5] cpufreq: schedutil: do not update rate limit ts when freq is unchanged Steve Muckle
2016-05-18 23:44 ` Rafael J. Wysocki
2016-05-19 19:46 ` Steve Muckle
2016-05-19 21:15 ` Rafael J. Wysocki
2016-05-19 23:34 ` Steve Muckle
2016-05-20 0:24 ` Rafael J. Wysocki
2016-05-20 0:37 ` Rafael J. Wysocki
2016-05-20 0:40 ` Steve Muckle
2016-05-20 0:46 ` Rafael J. Wysocki
2016-05-20 11:39 ` Rafael J. Wysocki
2016-05-20 11:54 ` Rafael J. Wysocki
2016-05-20 11:59 ` Rafael J. Wysocki
2016-05-20 0:37 ` Steve Muckle
2016-05-20 0:55 ` 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=20160519193547.GF17223@graphite.smuckle.net \
--to=steve.muckle@linaro.org \
--cc=Juri.Lelli@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=lenb@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=mturquette@baylibre.com \
--cc=patrick.bellasi@arm.com \
--cc=peterz@infradead.org \
--cc=rafael@kernel.org \
--cc=srinivas.pandruvada@linux.intel.com \
--cc=vincent.guittot@linaro.org \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).