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Date: Tue, 25 Jul 2017 07:03:36 +0000
From: Huaisheng HS1 Ye <yehs1@...ovo.com>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>
CC: "lenb@...nel.org" <lenb@...nel.org>,
"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
NingTing Cheng <chengnt@...ovo.com>
Subject: RE: [PATCH] cpufreq: intel_pstate: Fix cpuinfo_cur_freq after
performance governor changes
Hi Srinivas,
Your idea is great, but your patch at cpufreq.c will force all platforms to use scaling_cur_freq as first choice when userspace wants to access cpuinfo_cur_freq. It is ok for intel x86 platfrom but hard to say with other platforms.
I modified it like that, it looks more reasonable. How about that?
Hi Rafael,
Deleting "get" function pointer within intel_pstate would lead to sysfs interface cpuinfo_cur_freq disappearing, because of cpufreq_add_dev_interface will check "cpufreq_driver->get" for it.
Perhaps just return 0 with in intel_pstate_get would be a workaround for this issue, how about it?
I have tested this patch based on Purley platform, both Hardware and Software P-states works correct, we could get accurate and same frequency from cpuinfo_cur_freq and scaling_cur_freq.
drivers/cpufreq/cpufreq.c | 4 ++++
drivers/cpufreq/intel_pstate.c | 8 +++++---
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 9bf97a3..922f9d9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -694,6 +694,10 @@ static ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,
if (cur_freq)
return sprintf(buf, "%u\n", cur_freq);
+ cur_freq = arch_freq_get_on_cpu(policy->cpu);
+ if (cur_freq)
+ return sprintf(buf, "%u\n", cur_freq);
+
return sprintf(buf, "<unknown>\n");
}
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 6cd5035..33e6c10 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1924,9 +1924,11 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
static unsigned int intel_pstate_get(unsigned int cpu_num)
{
- struct cpudata *cpu = all_cpu_data[cpu_num];
-
- return cpu ? get_avg_frequency(cpu) : 0;
+ /*
+ * Use frequency from scaling_cur_freq, reserve this function
+ * for existing of sysfs cpuinfo_cur_freq.
+ */
+ return 0;
}
static void intel_pstate_set_update_util_hook(unsigned int cpu_num)
> On Tue, 2017-07-25 at 01:46 +0000, Huaisheng HS1 Ye wrote:
> > Hi Rafael,
> >
> > If you delete "get" function implement within intel_pstate, the sysfs
> > interface cpuinfo_cur_freq will display <unknown> all the time.
> cpuinfo_cur_freq by definition should show actual frequency HW frequency.
> Unless I missed something. So Len Brown's patch should also take care of this
> to get from arch specific function is available.
> So in addition to Rafael's change, what about this?
>
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index
> 9bf97a3..29ec687 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -689,8 +689,13 @@ store_one(scaling_max_freq, max);
> static ssize_t show_cpuinfo_cur_freq(struct cpufreq_policy *policy,
> char *buf)
> {
> - unsigned int cur_freq = __cpufreq_get(policy);
> + unsigned int cur_freq;
>
> + cur_freq = arch_freq_get_on_cpu(policy->cpu);
> + if (cur_freq)
> + return sprintf(buf, "%u\n", cur_freq);
> +
> + cur_freq = __cpufreq_get(policy);
> if (cur_freq)
> return sprintf(buf, "%u\n", cur_freq);
>
>
>
> Thanks,
> Srinivas
>
> > To be honest, at the beginning I have consider this way like you
> > patched, but based two reasons below, it is conservative for us to do
> > that.
> >
> > 1. I am worried about whether it would lead to confusion for customers
> > or Linux OS venders who are accustomed to cpuinfo_cur_freq.
> > 2. This is the first time for me to offer patch to intel_pstate, not
> > sure whether it could be accepted by you.
> >
> > >
> > > On Monday, July 24, 2017 03:32:47 PM Huaisheng HS1 Ye wrote:
> > > >
> > > > Hi Rafael,
> > > > Thanks for your reply.
> > > >
> > > > >
> > > > > On Monday, July 24, 2017 05:43:14 AM Huaisheng HS1 Ye wrote:
> > > > > >
> > > > > > After commit 82b4e03e01bc (intel_pstate: skip scheduler hook
> > > > > > when in "performance" mode) Software P-state control modes
> > > > > > couldn't get dynamic value during performance mode,
> > > > > Please explain what you mean here.
> > > > >
> > > > commit 82b4e03e01bc (intel_pstate: skip scheduler hook when in
> > > > "performance" mode) disables intel_pstate_set_update_util_hook
> > > > when current policy is performance within function
> > > > intel_pstate_set_policy.
> > > > It leads to Software P-states couldn't update sysfs interface
> > > > cpuinfo_cur_freq's value during performance mode, because of
> > > > pstate_funcs.update_util couldn't set for the given CPU.
> > > >
> > > > >
> > > > > I guess you carried out some tests and the results were not as
> > > > > expected, so what was the test?
> > > > Exactly, we check the sysfs interface cpuinfo_cur_freq and the
> > > > output of cpupower frequency-info both with performance mode.
> > > OK, so what about the change below:
> > >
> > > ---
> > > drivers/cpufreq/intel_pstate.c | 8 --------
> > > 1 file changed, 8 deletions(-)
> > >
> > > Index: linux-pm/drivers/cpufreq/intel_pstate.c
> > >
> ==============================================================
> > > =====
> > > --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> > > +++ linux-pm/drivers/cpufreq/intel_pstate.c
> > > @@ -1674,13 +1674,6 @@ static int intel_pstate_init_cpu(unsigne
> > > return 0;
> > > }
> > >
> > > -static unsigned int intel_pstate_get(unsigned int cpu_num) -{
> > > - struct cpudata *cpu = all_cpu_data[cpu_num];
> > > -
> > > - return cpu ? get_avg_frequency(cpu) : 0;
> > > -}
> > > -
> > > static void intel_pstate_set_update_util_hook(unsigned int
> > > cpu_num) {
> > > struct cpudata *cpu = all_cpu_data[cpu_num]; @@ -1921,7
> > > +1914,6 @@
> > > static struct cpufreq_driver intel_pstat
> > > .setpolicy = intel_pstate_set_policy,
> > > .suspend = intel_pstate_hwp_save_state,
> > > .resume = intel_pstate_resume,
> > > - .get = intel_pstate_get,
> > > .init = intel_pstate_cpu_init,
> > > .exit = intel_pstate_cpu_exit,
> > > .stop_cpu = intel_pstate_stop_cpu,
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