Re: [PATCH 12/15] hwmon, fam15h_power: introduce a cpu accumulated power reporting algorithm
From: Guenter Roeck
Date: Mon Aug 31 2015 - 00:31:03 EST
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 âcore power accumulatorâ 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@xxxxxxx>
---
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.
Thanks,
Guenter
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