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

Huang Rui
2015-08-31T13:10:43Z

On Sun, Aug 30, 2015 at 09:30:28PM -0700, Guenter Roeck wrote:
> On 08/30/2015 09:16 PM, Huang Rui wrote:
> >On Fri, Aug 28, 2015 at 07:05:13AM -0700, Guenter Roeck wrote:
> >>On 08/28/2015 03:45 AM, Huang Rui wrote:
> >>>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?
> >>>
> >>1 Joule = 1 Watt-second.
> >>
> >>Something else, though - did you make sure that your code doesn't overflow ?
> >>Even though you calculate the average in an u64, you display it as unsigned.
> >>
> >
> >Thanks to your reminder. It should not be overflow. The maximum power
> >consumption of processor (AMD CZ and future 15h) is about 15 Watts =
> >15,000,000 uWatts = 0xE4E1C0 uWatts, the size is 24 < 32 < 64 bits.
> >
> >Actually, the unit of jdelta is not Joule. Because the tdelta is the
> >loops (cycles) that PTSC counter (the freqency is about 100 MHz)
> >counts not seconds.
> >
> >So avg_acc is the average power consumption not the accumulated energy.
> >
>
> Would power1_average then be better suitable for the attribute ?
> There is also power1_average_interval which could be used to make
> the interval configurable.
>

power1_average and power1_average_interval looks better except we
might use a conversion that make interval from milliseconds to PTSC
cycles instead of "cat-ting" the sysfs file twice, right?

Thanks,
Rui