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, 8 Dec 2020 14:32:07 +0530 [thread overview]
Message-ID: <20201208090207.sz4v43bwvm7yugrb@vireshk-i7> (raw)
In-Reply-To: <146138074.tjdImvNTH2@kreacher>
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 ?
--
viresh
next prev parent reply other threads:[~2020-12-08 9:02 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 [this message]
2020-12-15 4:16 ` Viresh Kumar
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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