From: Viresh Kumar <viresh.kumar@linaro.org>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Linux PM <linux-pm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Doug Smythies <dsmythies@telus.net>,
Giovanni Gherdovich <ggherdovich@suse.com>
Subject: Re: [PATCH v1 3/4] cpufreq: Add special-purpose fast-switching callback for drivers
Date: Tue, 15 Dec 2020 09:46:36 +0530 [thread overview]
Message-ID: <20201215041636.yfgyswqjslg4hlff@vireshk-i7> (raw)
In-Reply-To: <20201208090207.sz4v43bwvm7yugrb@vireshk-i7>
On 08-12-20, 14:32, Viresh Kumar wrote:
> On 07-12-20, 17:35, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > First off, some cpufreq drivers (eg. intel_pstate) can pass hints
> > beyond the current target frequency to the hardware and there are no
> > provisions for doing that in the cpufreq framework. In particular,
> > today the driver has to assume that it should not allow the frequency
> > to fall below the one requested by the governor (or the required
> > capacity may not be provided) which may not be the case and which may
> > lead to excessive energy usage in some scenarios.
> >
> > Second, the hints passed by these drivers to the hardware need not be
> > in terms of the frequency, so representing the utilization numbers
> > coming from the scheduler as frequency before passing them to those
> > drivers is not really useful.
> >
> > Address the two points above by adding a special-purpose replacement
> > for the ->fast_switch callback, called ->adjust_perf, allowing the
> > governor to pass abstract performance level (rather than frequency)
> > values for the minimum (required) and target (desired) performance
> > along with the CPU capacity to compare them to.
> >
> > Also update the schedutil governor to use the new callback instead
> > of ->fast_switch if present.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > ---
> >
> > Changes with respect to the RFC:
> > - Don't pass "busy" to ->adjust_perf().
> > - Use a special 'update_util' hook for the ->adjust_perf() case in
> > schedutil (this still requires an additional branch because of the
> > shared common code between this case and the "frequency" one, but
> > IMV this version is cleaner nevertheless).
> >
> > ---
> > drivers/cpufreq/cpufreq.c | 40 ++++++++++++++++++++++++++++++++
> > include/linux/cpufreq.h | 14 +++++++++++
> > include/linux/sched/cpufreq.h | 5 ++++
> > kernel/sched/cpufreq_schedutil.c | 48 +++++++++++++++++++++++++++++++--------
> > 4 files changed, 98 insertions(+), 9 deletions(-)
> >
> > Index: linux-pm/include/linux/cpufreq.h
> > ===================================================================
> > --- linux-pm.orig/include/linux/cpufreq.h
> > +++ linux-pm/include/linux/cpufreq.h
> > @@ -320,6 +320,15 @@ struct cpufreq_driver {
> > unsigned int index);
> > unsigned int (*fast_switch)(struct cpufreq_policy *policy,
> > unsigned int target_freq);
> > + /*
> > + * ->fast_switch() replacement for drivers that use an internal
> > + * representation of performance levels and can pass hints other than
> > + * the target performance level to the hardware.
> > + */
> > + void (*adjust_perf)(unsigned int cpu,
> > + unsigned long min_perf,
> > + unsigned long target_perf,
> > + unsigned long capacity);
>
> With this callback in place, do we still need to keep the other stuff we
> introduced recently, like CPUFREQ_NEED_UPDATE_LIMITS ?
Ping
--
viresh
next prev parent reply other threads:[~2020-12-15 4:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 16:25 [PATCH v1 0/4] cpufreq: Allow drivers to receive more information from the governor Rafael J. Wysocki
2020-12-07 16:28 ` [PATCH v1 1/4] cpufreq: schedutil: Add util to struct sg_cpu Rafael J. Wysocki
2020-12-08 8:33 ` Viresh Kumar
2020-12-09 17:17 ` Rafael J. Wysocki
2020-12-07 16:29 ` [PATCH v1 2/4] cpufreq: schedutil: Adjust utilization instead of frequency Rafael J. Wysocki
2020-12-08 8:51 ` Viresh Kumar
2020-12-08 17:01 ` Rafael J. Wysocki
2020-12-09 5:16 ` Viresh Kumar
2020-12-09 15:32 ` Rafael J. Wysocki
2020-12-14 11:07 ` Viresh Kumar
2020-12-07 16:35 ` [PATCH v1 3/4] cpufreq: Add special-purpose fast-switching callback for drivers Rafael J. Wysocki
2020-12-08 9:02 ` Viresh Kumar
2020-12-15 4:16 ` Viresh Kumar [this message]
2020-12-15 15:38 ` Rafael J. Wysocki
2020-12-07 16:38 ` [PATCH v1 4/4] cpufreq: intel_pstate: Implement the ->adjust_perf() callback Rafael J. Wysocki
2020-12-08 12:43 ` Peter Zijlstra
2020-12-08 17:10 ` Rafael J. Wysocki
2020-12-08 16:30 ` [PATCH v1 0/4] cpufreq: Allow drivers to receive more information from the governor Giovanni Gherdovich
2020-12-08 17:13 ` Rafael J. Wysocki
2020-12-08 19:14 ` Doug Smythies
2020-12-13 19:12 ` Doug Smythies
2020-12-18 15:32 ` Peter Zijlstra
2020-12-14 20:01 ` [PATCH v2 0/3] " Rafael J. Wysocki
2020-12-14 20:04 ` [PATCH v2 1/3] cpufreq: schedutil: Add util to struct sg_cpu Rafael J. Wysocki
2020-12-14 20:08 ` [PATCH v2 2/3] cpufreq: Add special-purpose fast-switching callback for drivers Rafael J. Wysocki
2020-12-14 20:09 ` [PATCH v2 3/3] cpufreq: intel_pstate: Implement the ->adjust_perf() callback Rafael J. Wysocki
2020-12-15 3:29 ` Srinivas Pandruvada
2020-12-15 4:16 ` [PATCH v2 0/3] cpufreq: Allow drivers to receive more information from the governor Viresh Kumar
2020-12-17 15:26 ` Doug Smythies
2020-12-21 10:41 ` Rafael J. Wysocki
2020-12-18 16:11 ` Giovanni Gherdovich
2020-12-21 16:11 ` Rafael J. Wysocki
2020-12-23 13:06 ` Giovanni Gherdovich
2020-12-28 19:11 ` Rafael J. Wysocki
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