linux-kernel - Re: [RFT][Update][PATCH 2/2] cpufreq: intel_pstate: Update max CPU frequency on global turbo changes

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Date:   Tue, 05 Mar 2019 11:58:37 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Quentin Perret <quentin.perret@....com>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Chen Yu <yu.c.chen@...el.com>,
        Gabriele Mazzotta <gabriele.mzt@...il.com>,
        peterz@...radead.org
Subject: Re: [RFT][Update][PATCH 2/2] cpufreq: intel_pstate: Update max CPU frequency on global turbo changes

On Tuesday, March 5, 2019 11:50:56 AM CET Rafael J. Wysocki wrote:
> On Tuesday, March 5, 2019 11:42:59 AM CET Quentin Perret wrote:
> > Hi Rafael,
> > 
> > +CC Peter since we were talking about cpuinfo.*_freq recently.
> > 
> > On Friday 01 Mar 2019 at 13:57:06 (+0100), Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > While the cpuinfo.max_freq value doesn't really matter for
> > > intel_pstate in the active mode, in the passive mode it is used by
> > > governors as the maximum physical frequency of the CPU and the
> > > results of governor computations generally depend on it. Also it
> > > is made available to user space via sysfs and it should match the
> > > current HW configuration.
> > > 
> > > For this reason, make intel_pstate update cpuinfo.max_freq for all
> > > CPUs if it detects a global change of turbo frequency settings from
> > > "disable" to "enable" or the other way associated with a _PPC change
> > > notification from the platform firmware.
> > > 
> > > Note that policy_is_inactive() and cpufreq_set_policy() need to be
> > > made available to it for this purpose.
> > > 
> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=200759
> > > Reported-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > ---
> > > 
> > > Update, because the patch sent previously doesn't build, due to an extra
> > > arg declared for intel_pstate_update_max_freq().
> > > 
> > > ---
> > >  drivers/cpufreq/cpufreq.c      |   12 ++----------
> > >  drivers/cpufreq/intel_pstate.c |   33 ++++++++++++++++++++++++++++++++-
> > >  include/linux/cpufreq.h        |    7 +++++++
> > >  3 files changed, 41 insertions(+), 11 deletions(-)
> > > 
> > > Index: linux-pm/drivers/cpufreq/intel_pstate.c
> > > ===================================================================
> > > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> > > +++ linux-pm/drivers/cpufreq/intel_pstate.c
> > > @@ -897,6 +897,36 @@ static void intel_pstate_update_policies
> > >  		cpufreq_update_policy(cpu);
> > >  }
> > >  
> > > +static void intel_pstate_update_max_freq(unsigned int cpu)
> > > +{
> > > +	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> > > +	struct cpufreq_policy new_policy;
> > > +	struct cpudata *cpudata;
> > > +
> > > +	if (!policy)
> > > +		return;
> > > +
> > > +	down_write(&policy->rwsem);
> > > +
> > > +	if (policy_is_inactive(policy))
> > > +		goto unlock;
> > > +
> > > +	cpudata = all_cpu_data[cpu];
> > > +	policy->cpuinfo.max_freq = global.turbo_disabled_upd ?
> > > +			cpudata->pstate.max_freq : cpudata->pstate.turbo_freq;
> > > +
> > > +	memcpy(&new_policy, policy, sizeof(*policy));
> > > +	new_policy.max = min(policy->user_policy.max, policy->cpuinfo.max_freq);
> > > +	new_policy.min = min(policy->user_policy.min, new_policy.max);
> > > +
> > > +	cpufreq_set_policy(policy, &new_policy);
> > 
> > Do you want to force-restart the governor here ?
> 
> cpufreq_set_policy() is expected to take care of the governor.
> If it doesn't, there is a bug somewhere.
> 
> > Schedutil caches cpuinfo.max_freq for the iowait stuff in sugov_start() [1].
> 
> If it does so, it should update the cached value in sugov_limits().
> 
> I guess I can add a patch updating it to this series.

So after the Peter's patch "sched/cpufreq: Fix 32bit math overflow"
I will need to recompute sg_cpu->min in sugov_limits().

I'll wait for that patch from Peter to go in and repost the series on
top of it.