Re: [PATCH 12/15] hwmon, fam15h_power: introduce a cpu accumulated power reporting algorithm

[Huang Rui <ray.huang@amd.com>]

On Thu, Aug 27, 2015 at 10:30:43AM -0700, Guenter Roeck wrote:
> On Thu, Aug 27, 2015 at 04:07:43PM +0800, Huang Rui wrote:
> > This patch introduces an algorithm that computes the average power by
> > reading a delta value of “core power accumulator” register during
> > measurement interval, and then dividing delta value by the length of
> > the time interval.
> > 
> > User is able to use power1_acc entry to measure the processor power
> > consumption and power1_acc just needs to be read twice with an needed
> > interval in-between.
> > 
> > A simple example:
> > 
> > $ cat /sys/bus/pci/devices/0000\:00\:18.4/hwmon/hwmon0/power1_acc
> > $ sleep 10000s
> > $ cat /sys/bus/pci/devices/0000\:00\:18.4/hwmon/hwmon0/power1_acc
> > 
> > The result is current average processor power consumption in 10000
> > seconds. The unit of the result is uWatt.
> > 
> > Signed-off-by: Huang Rui <ray.huang@amd.com>
> > ---
> >  drivers/hwmon/fam15h_power.c | 62 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 62 insertions(+)
> > 
> > diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
> > index d529e4b..3bab797 100644
> > --- a/drivers/hwmon/fam15h_power.c
> > +++ b/drivers/hwmon/fam15h_power.c
> > @@ -60,6 +60,7 @@ struct fam15h_power_data {
> >  	u64 cu_acc_power[MAX_CUS];
> >  	/* performance timestamp counter */
> >  	u64 cpu_sw_pwr_ptsc[MAX_CUS];
> > +	struct mutex acc_pwr_mutex;
> >  };
> >  
> >  static ssize_t show_power(struct device *dev,
> > @@ -121,17 +122,74 @@ static DEVICE_ATTR(power1_crit, S_IRUGO, show_power_crit, NULL);
> >  static struct attribute_group fam15h_power_group;
> >  __ATTRIBUTE_GROUPS(fam15h_power);
> >  
> > +static ssize_t show_power_acc(struct device *dev,
> > +			      struct device_attribute *attr, char *buf)
> > +{
> > +	int cpu, cu, cu_num, cores_per_cu;
> > +	u64 curr_cu_acc_power[MAX_CUS],
> > +	    curr_ptsc[MAX_CUS], jdelta[MAX_CUS];
> > +	u64 tdelta, avg_acc;
> > +	struct fam15h_power_data *data = dev_get_drvdata(dev);
> > +
> > +	cores_per_cu = amd_get_cores_per_cu();
> > +	cu_num = boot_cpu_data.x86_max_cores / cores_per_cu;
> > +
> > +	for (cpu = 0, avg_acc = 0; cpu < cu_num * cores_per_cu; cpu += cores_per_cu) {
> > +		cu = cpu / cores_per_cu;
> > +		if (rdmsrl_safe_on_cpu(cpu, MSR_F15H_PTSC, &curr_ptsc[cu])) {
> > +			pr_err("Failed to read PTSC counter MSR on core%d\n",
> > +			       cpu);
> > +			return 0;
> > +		}
> > +
> > +		if (rdmsrl_safe_on_cpu(cpu, MSR_F15H_CU_PWR_ACCUMULATOR,
> > +				       &curr_cu_acc_power[cu])) {
> > +			pr_err("Failed to read compute unit power accumulator MSR on core%d\n",
> > +			       cpu);
> > +			return 0;
> > +		}
> > +
> > +		if (curr_cu_acc_power[cu] < data->cu_acc_power[cu]) {
> > +			jdelta[cu] = data->max_cu_acc_power + curr_cu_acc_power[cu];
> > +			jdelta[cu] -= data->cu_acc_power[cu];
> > +		} else {
> > +			jdelta[cu] = curr_cu_acc_power[cu] - data->cu_acc_power[cu];
> > +		}
> > +		tdelta = curr_ptsc[cu] - data->cpu_sw_pwr_ptsc[cu];
> > +		jdelta[cu] *= data->cpu_pwr_sample_ratio * 1000;
> > +		do_div(jdelta[cu], tdelta);
> > +
> > +		mutex_lock(&data->acc_pwr_mutex);
> > +		data->cu_acc_power[cu] = curr_cu_acc_power[cu];
> > +		data->cpu_sw_pwr_ptsc[cu] = curr_ptsc[cu];
> > +		mutex_unlock(&data->acc_pwr_mutex);
> > +
> > +		/* the unit is microWatt */
> > +		avg_acc += jdelta[cu];
> > +	}
> > +
> > +	return sprintf(buf, "%u\n", (unsigned int) avg_acc);
> > +}
> > +static DEVICE_ATTR(power1_acc, S_IRUGO, show_power_acc, NULL);
> 
> I am not really a friend of introducing a non-standard attribute.
> Does the energy attribute not work here ?
> 

You're right. Non-standard attribute might not be good. Could you
please give me some hints if I use "energy" instead?

Thanks,
Rui