linux-kernel - Re: [PATCH v5 2/6] hwmon: (fam15h_power) Add compute unit accumulated power

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Message-ID: <20160328092952.GB26651@pd.tnic>
Date:	Mon, 28 Mar 2016 11:29:52 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Huang Rui <ray.huang@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Guenter Roeck <linux@...ck-us.net>,
	Jean Delvare <jdelvare@...e.de>, linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org, spg_linux_kernel@....com
Subject: Re: [PATCH v5 2/6] hwmon: (fam15h_power) Add compute unit
 accumulated power

On Mon, Mar 28, 2016 at 01:32:12PM +0800, Huang Rui wrote:
> This patch adds a member in fam15h_power_data which specifies the
> compute unit accumulated power. It adds do_read_registers_on_cu to do
> all the read to all MSRs and run it on one of the online cores on each
> compute unit with smp_call_function_many(). This behavior can decrease
> IPI numbers.
> 
> Suggested-by: Borislav Petkov <bp@...en8.de>
> Signed-off-by: Huang Rui <ray.huang@....com>
> ---
>  drivers/hwmon/fam15h_power.c | 65 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
> index 4f695d8..ccbc944 100644
> --- a/drivers/hwmon/fam15h_power.c
> +++ b/drivers/hwmon/fam15h_power.c
> @@ -25,6 +25,8 @@
>  #include <linux/module.h>
>  #include <linux/pci.h>
>  #include <linux/bitops.h>
> +#include <linux/cpu.h>
> +#include <linux/cpumask.h>
>  #include <asm/processor.h>
>  #include <asm/msr.h>
>  
> @@ -44,7 +46,9 @@ MODULE_LICENSE("GPL");
>  
>  #define FAM15H_MIN_NUM_ATTRS		2
>  #define FAM15H_NUM_GROUPS		2
> +#define MAX_CUS				8
>  
> +#define MSR_F15H_CU_PWR_ACCUMULATOR	0xc001007a
>  #define MSR_F15H_CU_MAX_PWR_ACCUMULATOR	0xc001007b
>  
>  #define PCI_DEVICE_ID_AMD_15H_M70H_NB_F4 0x15b4
> @@ -59,6 +63,8 @@ struct fam15h_power_data {
>  	struct attribute_group group;
>  	/* maximum accumulated power of a compute unit */
>  	u64 max_cu_acc_power;
> +	/* accumulated power of the compute units */
> +	u64 cu_acc_power[MAX_CUS];
>  };
>  
>  static ssize_t show_power(struct device *dev,
> @@ -125,6 +131,63 @@ static ssize_t show_power_crit(struct device *dev,
>  }
>  static DEVICE_ATTR(power1_crit, S_IRUGO, show_power_crit, NULL);
>  
> +static void do_read_registers_on_cu(void *_data)
> +{
> +	struct fam15h_power_data *data = _data;
> +	int cpu, cu;
> +
> +	cpu = smp_processor_id();
> +
> +	/*
> +	 * With the new x86 topology modelling, cpu core id actually
> +	 * is compute unit id.
> +	 */
> +	cu = cpu_data(cpu).cpu_core_id;
> +
> +	rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR, &data->cu_acc_power[cu]);
> +}
> +
> +/*
> + * This function is only able to be called when CPUID
> + * Fn8000_0007:EDX[12] is set.
> + */
> +static int read_registers(struct fam15h_power_data *data)
> +{
> +	int this_cpu, ret, cpu;
> +	int target;
> +	cpumask_var_t mask;
> +
> +	ret = zalloc_cpumask_var(&mask, GFP_KERNEL);
> +	if (!ret)
> +		return -ENOMEM;
> +
> +	get_online_cpus();
> +	this_cpu = get_cpu();

What now?

get_online_cpus() is enough.

> +
> +	/*
> +	 * Choose the first online core of each compute unit, and then
> +	 * read their MSR value of power and ptsc in a single IPI,
> +	 * because the MSR value of CPU core represent the compute
> +	 * unit's.
> +	 */
> +	for_each_online_cpu(cpu) {
> +		target = cpumask_first(topology_sibling_cpumask(cpu));
> +		if (!cpumask_test_cpu(target, mask))
> +			cpumask_set_cpu(target, mask);
> +	}

I think you want something like this: iterate over each core and put one
of them into the mask.

	core = -1;

	for_each_online_cpu(cpu) {
		this_core = topology_core_id(cpu);

		if (this_core == core)
			continue;

		core = this_core;

		/* get any CPU on this compute unit */
		cpumask_set_cpu(cpumask_any(topology_sibling_cpumask(cpu)), mask);
	}


Btw, tglx, peterz, do you guys think it would make sense to have a
generic helper:

	for_each_core(cpu)

which would give you any of the threads on the core in the @cpu var when
iterating?

I see only arch/x86/events/intel/cstate.c doing any comparisons with
topology_core_id() now but it might be useful...

-- 
Regards/Gruss,
    Boris.

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