Messages in this thread | | | Subject | Re: [PATCH v2 07/10] hwmon: (fam15h_power) Introduce a cpu accumulated power reporting algorithm | From | Guenter Roeck <> | Date | Fri, 23 Oct 2015 07:20:59 -0700 |
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On 10/19/2015 07:28 PM, 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_average entry to measure the processor power > consumption and power1_average_interval entry to set the interval. > > A simple example: > > ray@hr-ub:~/tip$ sensors > fam15h_power-pci-00c4 > Adapter: PCI adapter > power1: 23.73 mW (avg = 634.63 mW, interval = 0.01 s) > (crit = 15.00 W) > > ... > > The result is current average processor power consumption in 10 > millisecond. The unit of the result is uWatt. > > Suggested-by: Guenter Roeck <linux@roeck-us.net> > Signed-off-by: Huang Rui <ray.huang@amd.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@kernel.org> > --- > drivers/hwmon/fam15h_power.c | 120 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 120 insertions(+) > > diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c > index 6321f73..a5a539e 100644 > --- a/drivers/hwmon/fam15h_power.c > +++ b/drivers/hwmon/fam15h_power.c > @@ -26,6 +26,9 @@ > #include <linux/pci.h> > #include <linux/bitops.h> > #include <linux/cpumask.h> > +#include <linux/mutex.h> > +#include <linux/time.h> > +#include <linux/sched.h> > #include <asm/processor.h> > #include <asm/msr.h> > > @@ -64,6 +67,10 @@ struct fam15h_power_data { > u64 cu_acc_power[MAX_CUS]; > /* performance timestamp counter */ > u64 cpu_sw_pwr_ptsc[MAX_CUS]; > + /* online/offline status of current compute unit */ > + int cu_on[MAX_CUS]; > + unsigned long power_period; > + struct mutex acc_pwr_mutex;
Can you elaborate a bit about what this mutex is supposed to protect ? To me it seems that it doesn't really protect anything.
> }; > > static ssize_t show_power(struct device *dev, > @@ -132,11 +139,15 @@ static void do_read_registers_on_cu(void *_data) > cores_per_cu = amd_get_cores_per_cu(); > cu = cpu / cores_per_cu; > > + mutex_lock(&data->acc_pwr_mutex); > WARN_ON(rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR, > &data->cu_acc_power[cu])); > > WARN_ON(rdmsrl_safe(MSR_F15H_PTSC, > &data->cpu_sw_pwr_ptsc[cu])); > + > + data->cu_on[cu] = 1; > + mutex_unlock(&data->acc_pwr_mutex);
... for example, while this protects cu_on[cu],
> } > > static int read_registers(struct fam15h_power_data *data) > @@ -148,6 +159,10 @@ static int read_registers(struct fam15h_power_data *data) > cores_per_cu = amd_get_cores_per_cu(); > cu_num = boot_cpu_data.x86_max_cores / cores_per_cu; > > + mutex_lock(&data->acc_pwr_mutex); > + memset(data->cu_on, 0, sizeof(int) * MAX_CUS); > + mutex_unlock(&data->acc_pwr_mutex);
... this code may well overwrite that same value.
> + > WARN_ON_ONCE(cu_num > MAX_CUS); > > ret = zalloc_cpumask_var(&mask, GFP_KERNEL); > @@ -184,18 +199,113 @@ static int read_registers(struct fam15h_power_data *data) > return 0; > } > > +static ssize_t acc_show_power(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + struct fam15h_power_data *data = dev_get_drvdata(dev); > + u64 prev_cu_acc_power[MAX_CUS], prev_ptsc[MAX_CUS], > + jdelta[MAX_CUS]; > + u64 tdelta, avg_acc; > + int cu, cu_num, cores_per_cu, ret; > + signed long leftover; > + > + cores_per_cu = amd_get_cores_per_cu(); > + cu_num = boot_cpu_data.x86_max_cores / cores_per_cu; > + > + ret = read_registers(data); > + if (ret) > + return 0; > + > + cu = 0; > + while(cu++ < cu_num) { > + prev_cu_acc_power[cu] = data->cu_acc_power[cu]; > + prev_ptsc[cu] = data->cpu_sw_pwr_ptsc[cu]; > + }
... and multiple parallel reads on the power attribute must produce pretty random values, unless I am really missing something.
> + > + leftover = schedule_timeout_interruptible( > + msecs_to_jiffies(data->power_period) > + ); > + if (leftover) > + return 0; > + > + ret = read_registers(data); > + if (ret) > + return 0; > + With a 10ms period, I wonder how accurate this really is.
> + for (cu = 0, avg_acc = 0; cu < cu_num; cu++) { > + /* check if current compute unit is online */ > + if (data->cu_on[cu] == 0) > + continue; > + > + if (data->cu_acc_power[cu] < prev_cu_acc_power[cu]) { > + jdelta[cu] = data->max_cu_acc_power + data->cu_acc_power[cu]; > + jdelta[cu] -= prev_cu_acc_power[cu]; > + } else { > + jdelta[cu] = data->cu_acc_power[cu] - prev_cu_acc_power[cu]; > + } > + tdelta = data->cpu_sw_pwr_ptsc[cu] - prev_ptsc[cu]; > + jdelta[cu] *= data->cpu_pwr_sample_ratio * 1000; > + do_div(jdelta[cu], tdelta); > + > + /* the unit is microWatt */ > + avg_acc += jdelta[cu]; > + } > + > + return sprintf(buf, "%llu\n", (unsigned long long)avg_acc); > +} > +static DEVICE_ATTR(power1_average, S_IRUGO, acc_show_power, NULL); > + > + > +static ssize_t acc_show_power_period(struct device *dev, > + struct device_attribute *attr, > + char *buf) > +{ > + struct fam15h_power_data *data = dev_get_drvdata(dev); > + > + return sprintf(buf, "%lu\n", data->power_period); > +} > + > +static ssize_t acc_set_power_period(struct device *dev, > + struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct fam15h_power_data *data = dev_get_drvdata(dev); > + unsigned long temp; > + int ret; > + > + ret = kstrtoul(buf, 10, &temp); > + if (ret) > + return ret; > + > + mutex_lock(&data->acc_pwr_mutex); > + data->power_period = temp; > + mutex_unlock(&data->acc_pwr_mutex);
This doesn't really protect anything either except that power_period can not be updated while the lock is active. But the code using power_period does not run under mutex protection, so that seems pretty pointless.
Also, this accepts an unlimited timeout. If I understand correctly, setting the timeout to, say, 10 seconds will cause the read function to hang for that period of time. Setting it to 1 hour will cause the read function to hang for 1 hour.
Does this really make sense ?
> + > + return count; > +} > +static DEVICE_ATTR(power1_average_interval, S_IRUGO | S_IWUSR, > + acc_show_power_period, acc_set_power_period); > + > static int fam15h_power_init_attrs(struct pci_dev *pdev, > struct fam15h_power_data *data) > { > int n = FAM15H_MIN_NUM_ATTRS; > struct attribute **fam15h_power_attrs; > struct cpuinfo_x86 *c = &boot_cpu_data; > + u32 cpuid; > > if (c->x86 == 0x15 && > ((c->x86_model <= 0xf) || > (c->x86_model >= 0x60 && c->x86_model <= 0x6f))) > n += 1; > > + cpuid = cpuid_edx(0x80000007); > + > + /* check if processor supports accumulated power */ > + if (cpuid & BIT(12)) > + n += 2; > + > fam15h_power_attrs = devm_kcalloc(&pdev->dev, n, > sizeof(*fam15h_power_attrs), > GFP_KERNEL); > @@ -210,6 +320,11 @@ static int fam15h_power_init_attrs(struct pci_dev *pdev, > (c->x86_model >= 0x60 && c->x86_model <= 0x6f))) > fam15h_power_attrs[n++] = &dev_attr_power1_input.attr; > > + if (cpuid & BIT(12)) { > + fam15h_power_attrs[n++] = &dev_attr_power1_average.attr; > + fam15h_power_attrs[n++] = &dev_attr_power1_average_interval.attr; > + } > + > data->fam15h_power_group.attrs = fam15h_power_attrs; > > return 0; > @@ -322,6 +437,9 @@ static int fam15h_power_init_data(struct pci_dev *f4, > > data->max_cu_acc_power = tmp; > > + /* set default interval as 10 ms */ > + data->power_period = 10; > + > ret = read_registers(data); > > return ret; > @@ -349,6 +467,8 @@ static int fam15h_power_probe(struct pci_dev *pdev, > if (!data) > return -ENOMEM; > > + mutex_init(&data->acc_pwr_mutex); > + > ret = fam15h_power_init_data(pdev, data); > if (ret) > return ret; >
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