On Mon, Aug 31, 2015 at 03:25:35PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 27, 2015 at 04:07:43PM +0800, Huang Rui wrote:
> > +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);
>
> This is a world readable file that sprays IPIs across the entire system,
> how is that a good idea?
FWIW this driver is also hotplug challenged. Not to mention it relies on
cpu number layout in unhealthy ways.
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