linux-kernel - Re: [PATCH v2 05/10] hwmon: (fam15h_power) Add compute unit accumulated power

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Date:	Fri, 23 Oct 2015 06:37:22 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Borislav Petkov <bp@...e.de>, Huang Rui <ray.huang@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Jean Delvare <jdelvare@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Andreas Herrmann <herrmann.der.user@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	lm-sensors@...sensors.org, linux-kernel@...r.kernel.org,
	x86@...nel.org,
	Andreas Herrmann <herrmann.der.user@...glemail.com>,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>, Tony Li <tony.li@....com>
Subject: Re: [PATCH v2 05/10] hwmon: (fam15h_power) Add compute unit
 accumulated power

On 10/23/2015 06:27 AM, Borislav Petkov wrote:
> On Tue, Oct 20, 2015 at 10:28:24AM +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>
>> Cc: Guenter Roeck <linux@...ck-us.net>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> ---
>>   drivers/hwmon/fam15h_power.c | 68 +++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 67 insertions(+), 1 deletion(-)
>>

[ ... ]

>> +static void do_read_registers_on_cu(void *_data)
>> +{
>> +	struct fam15h_power_data *data = _data;
>> +	int cpu, cu, cores_per_cu;
>> +
>> +	cpu = smp_processor_id();
>> +
>> +	cores_per_cu = amd_get_cores_per_cu();
>> +	cu = cpu / cores_per_cu;
>> +
>> +	WARN_ON(rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR,
>> +			    &data->cu_acc_power[cu]));
>
> I guess the WARN_ON's here should be WARN_ON_ONCE() - otherwise dmesg is
> filling up very quickly.
>
I don't really understand why WARN_ON (or WARN_ON_ONCE)
would be warranted here in the first place.

Guenter

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