Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752636AbbH1OFV (ORCPT ); Fri, 28 Aug 2015 10:05:21 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:45151 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752106AbbH1OFT (ORCPT ); Fri, 28 Aug 2015 10:05:19 -0400 Message-ID: <55E06A99.7070800@roeck-us.net> Date: Fri, 28 Aug 2015 07:05:13 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Huang Rui CC: Borislav Petkov , Jean Delvare , Andy Lutomirski , Andreas Herrmann , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , "Rafael J. Wysocki" , Len Brown , John Stultz , =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= , lm-sensors@lm-sensors.org, linux-kernel@vger.kernel.org, x86@kernel.org, Andreas Herrmann , Aravind Gopalakrishnan , Borislav Petkov , Fengguang Wu , Aaron Lu , Tony Li Subject: Re: [PATCH 12/15] hwmon, fam15h_power: introduce a cpu accumulated power reporting algorithm References: <1440662866-28716-1-git-send-email-ray.huang@amd.com> <1440662866-28716-13-git-send-email-ray.huang@amd.com> <20150827173043.GB27452@roeck-us.net> <20150828104525.GD4191@hr-slim.amd.com> In-Reply-To: <20150828104525.GD4191@hr-slim.amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=0.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4559 Lines: 120 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 “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_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 >>> --- >>> 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. 100w * 10,000s = 1,000,000ws = 1,000,000,000,000 micro-watt-seconds, which is a bit large for an unsigned. Also, the values should not be reset after reading, but accumulate. Also, I think your code may be vulnerable to overflows on the CPU register side. How long does it take before the CPU counters overflow ? Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/