Re: [PATCH] cpufreq, intel_pstate, Fix intel_pstate powersave min_perf_pct value

[Prarit Bhargava]

On 10/14/2015 05:09 PM, Kristen Carlson Accardi wrote:
> On Wed, 14 Oct 2015 07:41:59 -0400
> Prarit Bhargava <prarit@xxxxxxxxxx> wrote:
> 
>> On systems that initialize the intel_pstate driver with the performance
>> governor, and then switch to the powersave governor will not transition to
>> lower cpu frequencies until /sys/devices/system/cpu/intel_pstate/min_perf_pct
>> is set to a low value.
>>
>> The behavior of governor switching changed after commit a04759924e25
>> ("[cpufreq] intel_pstate: honor user space min_perf_pct override on
>>  resume").  The commit introduced tracking of performance percentage
>> changes via sysfs in order to restore userspace changes during
>> suspend/resume.  The problem occurs because the global values of the newly
>> introduced max_sysfs_pct and min_sysfs_pct are not lowered on the governor
>> change and this causes the powersave governor to inherit the performance
>> governor's settings.
>>
>> A simple change would have been to reset max_sysfs_pct to 100 and
>> min_sysfs_pct to 0 on a governor change, which fixes the problem with
>> governor switching.  However, since we cannot break userspace[1] the fix
>> is now to give each governor its own limits storage area so that governor
>> specific changes are tracked.
>>
>> I successfully tested this by booting with both the performance governor
>> and the powersave governor by default, and switching between the two
>> governors (while monitoring /sys/devices/system/cpu/intel_pstate/ values,
>> and looking at the output of cpupower frequency-info).  Suspend/Resume
>> testing was performed by Doug Smythies.
>>
>> [1] Systems which suspend/resume using the unmaintained pm-utils package
>> will always transition to the performance governor before the suspend and
>> after the resume.  This means a system using the powersave governor will
>> go from powersave to performance, then suspend/resume, performance to
>> powersave.  The simple change during governor changes would have been
>> overwritten when the governor changed before and after the suspend/resume.
>> I have submitted https://bugzilla.redhat.com/show_bug.cgi?id=1271225
>> against Fedora to remove the 94cpufreq file that causes the problem.  It
>> should be noted that pm-utils is obsoleted with newer versions of systemd.
>>
>> Cc: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
>> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
>> Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
>> Cc: linux-pm@xxxxxxxxxxxxxxx
>> Cc: Doug Smythies <dsmythies@xxxxxxxxx>
>> Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
> 
> Acked-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
> 
> BTW - I think I can see an issue here with HWP enabled systems.  It
> looks to me like the hwp settings will not be programmed correctly
> during a governor switch.  This probably needs to be addressed in a
> separate patch.
> 

Oh, I see it now too.  I'll get to that in another patch.  Thanks for pointing
that out Kristen.

P.

>> ---
>>  drivers/cpufreq/intel_pstate.c |  120 +++++++++++++++++++++++++---------------
>>  1 file changed, 75 insertions(+), 45 deletions(-)
>>
>> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
>> index 3af9dd7..78b4be5 100644
>> --- a/drivers/cpufreq/intel_pstate.c
>> +++ b/drivers/cpufreq/intel_pstate.c
>> @@ -156,7 +156,20 @@ struct perf_limits {
>>  	int min_sysfs_pct;
>>  };
>>  
>> -static struct perf_limits limits = {
>> +static struct perf_limits performance_limits = {
>> +	.no_turbo = 0,
>> +	.turbo_disabled = 0,
>> +	.max_perf_pct = 100,
>> +	.max_perf = int_tofp(1),
>> +	.min_perf_pct = 100,
>> +	.min_perf = int_tofp(1),
>> +	.max_policy_pct = 100,
>> +	.max_sysfs_pct = 100,
>> +	.min_policy_pct = 0,
>> +	.min_sysfs_pct = 0,
>> +};
>> +
>> +static struct perf_limits powersave_limits = {
>>  	.no_turbo = 0,
>>  	.turbo_disabled = 0,
>>  	.max_perf_pct = 100,
>> @@ -169,6 +182,12 @@ static struct perf_limits limits = {
>>  	.min_sysfs_pct = 0,
>>  };
>>  
>> +#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE
>> +static struct perf_limits *limits = &performance_limits;
>> +#else
>> +static struct perf_limits *limits = &powersave_limits;
>> +#endif
>> +
>>  static inline void pid_reset(struct _pid *pid, int setpoint, int busy,
>>  			     int deadband, int integral) {
>>  	pid->setpoint = setpoint;
>> @@ -255,7 +274,7 @@ static inline void update_turbo_state(void)
>>  
>>  	cpu = all_cpu_data[0];
>>  	rdmsrl(MSR_IA32_MISC_ENABLE, misc_en);
>> -	limits.turbo_disabled =
>> +	limits->turbo_disabled =
>>  		(misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE ||
>>  		 cpu->pstate.max_pstate == cpu->pstate.turbo_pstate);
>>  }
>> @@ -274,14 +293,14 @@ static void intel_pstate_hwp_set(void)
>>  
>>  	for_each_online_cpu(cpu) {
>>  		rdmsrl_on_cpu(cpu, MSR_HWP_REQUEST, &value);
>> -		adj_range = limits.min_perf_pct * range / 100;
>> +		adj_range = limits->min_perf_pct * range / 100;
>>  		min = hw_min + adj_range;
>>  		value &= ~HWP_MIN_PERF(~0L);
>>  		value |= HWP_MIN_PERF(min);
>>  
>> -		adj_range = limits.max_perf_pct * range / 100;
>> +		adj_range = limits->max_perf_pct * range / 100;
>>  		max = hw_min + adj_range;
>> -		if (limits.no_turbo) {
>> +		if (limits->no_turbo) {
>>  			hw_max = HWP_GUARANTEED_PERF(cap);
>>  			if (hw_max < max)
>>  				max = hw_max;
>> @@ -350,7 +369,7 @@ static void __init intel_pstate_debug_expose_params(void)
>>  	static ssize_t show_##file_name					\
>>  	(struct kobject *kobj, struct attribute *attr, char *buf)	\
>>  	{								\
>> -		return sprintf(buf, "%u\n", limits.object);		\
>> +		return sprintf(buf, "%u\n", limits->object);		\
>>  	}
>>  
>>  static ssize_t show_turbo_pct(struct kobject *kobj,
>> @@ -386,10 +405,10 @@ static ssize_t show_no_turbo(struct kobject *kobj,
>>  	ssize_t ret;
>>  
>>  	update_turbo_state();
>> -	if (limits.turbo_disabled)
>> -		ret = sprintf(buf, "%u\n", limits.turbo_disabled);
>> +	if (limits->turbo_disabled)
>> +		ret = sprintf(buf, "%u\n", limits->turbo_disabled);
>>  	else
>> -		ret = sprintf(buf, "%u\n", limits.no_turbo);
>> +		ret = sprintf(buf, "%u\n", limits->no_turbo);
>>  
>>  	return ret;
>>  }
>> @@ -405,12 +424,12 @@ static ssize_t store_no_turbo(struct kobject *a, struct attribute *b,
>>  		return -EINVAL;
>>  
>>  	update_turbo_state();
>> -	if (limits.turbo_disabled) {
>> +	if (limits->turbo_disabled) {
>>  		pr_warn("intel_pstate: Turbo disabled by BIOS or unavailable on processor\n");
>>  		return -EPERM;
>>  	}
>>  
>> -	limits.no_turbo = clamp_t(int, input, 0, 1);
>> +	limits->no_turbo = clamp_t(int, input, 0, 1);
>>  
>>  	if (hwp_active)
>>  		intel_pstate_hwp_set();
>> @@ -428,11 +447,15 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b,
>>  	if (ret != 1)
>>  		return -EINVAL;
>>  
>> -	limits.max_sysfs_pct = clamp_t(int, input, 0 , 100);
>> -	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
>> -	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
>> -	limits.max_perf_pct = max(limits.min_perf_pct, limits.max_perf_pct);
>> -	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
>> +	limits->max_sysfs_pct = clamp_t(int, input, 0 , 100);
>> +	limits->max_perf_pct = min(limits->max_policy_pct,
>> +				   limits->max_sysfs_pct);
>> +	limits->max_perf_pct = max(limits->min_policy_pct,
>> +				   limits->max_perf_pct);
>> +	limits->max_perf_pct = max(limits->min_perf_pct,
>> +				   limits->max_perf_pct);
>> +	limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
>> +				  int_tofp(100));
>>  
>>  	if (hwp_active)
>>  		intel_pstate_hwp_set();
>> @@ -449,11 +472,15 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
>>  	if (ret != 1)
>>  		return -EINVAL;
>>  
>> -	limits.min_sysfs_pct = clamp_t(int, input, 0 , 100);
>> -	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
>> -	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
>> -	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);
>> -	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
>> +	limits->min_sysfs_pct = clamp_t(int, input, 0 , 100);
>> +	limits->min_perf_pct = max(limits->min_policy_pct,
>> +				   limits->min_sysfs_pct);
>> +	limits->min_perf_pct = min(limits->max_policy_pct,
>> +				   limits->min_perf_pct);
>> +	limits->min_perf_pct = min(limits->max_perf_pct,
>> +				   limits->min_perf_pct);
>> +	limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
>> +				  int_tofp(100));
>>  
>>  	if (hwp_active)
>>  		intel_pstate_hwp_set();
>> @@ -533,7 +560,7 @@ static void byt_set_pstate(struct cpudata *cpudata, int pstate)
>>  	u32 vid;
>>  
>>  	val = (u64)pstate << 8;
>> -	if (limits.no_turbo && !limits.turbo_disabled)
>> +	if (limits->no_turbo && !limits->turbo_disabled)
>>  		val |= (u64)1 << 32;
>>  
>>  	vid_fp = cpudata->vid.min + mul_fp(
>> @@ -622,7 +649,7 @@ static void core_set_pstate(struct cpudata *cpudata, int pstate)
>>  	u64 val;
>>  
>>  	val = (u64)pstate << 8;
>> -	if (limits.no_turbo && !limits.turbo_disabled)
>> +	if (limits->no_turbo && !limits->turbo_disabled)
>>  		val |= (u64)1 << 32;
>>  
>>  	wrmsrl_on_cpu(cpudata->cpu, MSR_IA32_PERF_CTL, val);
>> @@ -702,7 +729,7 @@ static void intel_pstate_get_min_max(struct cpudata *cpu, int *min, int *max)
>>  	int max_perf_adj;
>>  	int min_perf;
>>  
>> -	if (limits.no_turbo || limits.turbo_disabled)
>> +	if (limits->no_turbo || limits->turbo_disabled)
>>  		max_perf = cpu->pstate.max_pstate;
>>  
>>  	/*
>> @@ -710,11 +737,11 @@ static void intel_pstate_get_min_max(struct cpudata *cpu, int *min, int *max)
>>  	 * policy, or by cpu specific default values determined through
>>  	 * experimentation.
>>  	 */
>> -	max_perf_adj = fp_toint(mul_fp(int_tofp(max_perf), limits.max_perf));
>> +	max_perf_adj = fp_toint(mul_fp(int_tofp(max_perf), limits->max_perf));
>>  	*max = clamp_t(int, max_perf_adj,
>>  			cpu->pstate.min_pstate, cpu->pstate.turbo_pstate);
>>  
>> -	min_perf = fp_toint(mul_fp(int_tofp(max_perf), limits.min_perf));
>> +	min_perf = fp_toint(mul_fp(int_tofp(max_perf), limits->min_perf));
>>  	*min = clamp_t(int, min_perf, cpu->pstate.min_pstate, max_perf);
>>  }
>>  
>> @@ -988,32 +1015,35 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>>  
>>  	if (policy->policy == CPUFREQ_POLICY_PERFORMANCE &&
>>  	    policy->max >= policy->cpuinfo.max_freq) {
>> -		limits.min_policy_pct = 100;
>> -		limits.min_perf_pct = 100;
>> -		limits.min_perf = int_tofp(1);
>> -		limits.max_policy_pct = 100;
>> -		limits.max_perf_pct = 100;
>> -		limits.max_perf = int_tofp(1);
>> -		limits.no_turbo = 0;
>> +		pr_debug("intel_pstate: set performance\n");
>> +		limits = &performance_limits;
>>  		return 0;
>>  	}
>>  
>> -	limits.min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
>> -	limits.min_policy_pct = clamp_t(int, limits.min_policy_pct, 0 , 100);
>> -	limits.max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
>> -	limits.max_policy_pct = clamp_t(int, limits.max_policy_pct, 0 , 100);
>> +	pr_debug("intel_pstate: set powersave\n");
>> +	limits = &powersave_limits;
>> +	limits->min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
>> +	limits->min_policy_pct = clamp_t(int, limits->min_policy_pct, 0 , 100);
>> +	limits->max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
>> +	limits->max_policy_pct = clamp_t(int, limits->max_policy_pct, 0 , 100);
>>  
>>  	/* Normalize user input to [min_policy_pct, max_policy_pct] */
>> -	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
>> -	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
>> -	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
>> -	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
>> +	limits->min_perf_pct = max(limits->min_policy_pct,
>> +				   limits->min_sysfs_pct);
>> +	limits->min_perf_pct = min(limits->max_policy_pct,
>> +				   limits->min_perf_pct);
>> +	limits->max_perf_pct = min(limits->max_policy_pct,
>> +				   limits->max_sysfs_pct);
>> +	limits->max_perf_pct = max(limits->min_policy_pct,
>> +				   limits->max_perf_pct);
>>  
>>  	/* Make sure min_perf_pct <= max_perf_pct */
>> -	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);
>> +	limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
>>  
>> -	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
>> -	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
>> +	limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
>> +				  int_tofp(100));
>> +	limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
>> +				  int_tofp(100));
>>  
>>  	if (hwp_active)
>>  		intel_pstate_hwp_set();
>> @@ -1057,7 +1087,7 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
>>  
>>  	cpu = all_cpu_data[policy->cpu];
>>  
>> -	if (limits.min_perf_pct == 100 && limits.max_perf_pct == 100)
>> +	if (limits->min_perf_pct == 100 && limits->max_perf_pct == 100)
>>  		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
>>  	else
>>  		policy->policy = CPUFREQ_POLICY_POWERSAVE;
> 
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