From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753577AbbIAQHB (ORCPT ); Tue, 1 Sep 2015 12:07:01 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:58287 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbbIAQHA (ORCPT ); Tue, 1 Sep 2015 12:07:00 -0400 Message-ID: <55E5CD1C.4070502@roeck-us.net> Date: Tue, 01 Sep 2015 09:06:52 -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: Borislav Petkov CC: Peter Zijlstra , Ingo Molnar , Huang Rui , Borislav Petkov , Jean Delvare , Andy Lutomirski , Andreas Herrmann , Thomas Gleixner , "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 , Fengguang Wu , Aaron Lu , Tony Li Subject: Re: [PATCH 09/15] x86, amd: add accessor for number of cores per compute unit References: <1440662866-28716-10-git-send-email-ray.huang@amd.com> <20150828064814.GB20153@nazgul.tnic> <20150828080418.GB13309@gmail.com> <20150829091914.GA8878@gmail.com> <20150830155322.GA26370@nazgul.tnic> <20150831083821.GE16853@twins.programming.kicks-ass.net> <20150831160622.GA29830@nazgul.tnic> <55E47E88.7080202@roeck-us.net> <20150831204426.GI16853@twins.programming.kicks-ass.net> <55E4C5F8.6050303@roeck-us.net> <20150901155600.GA8497@nazgul.tnic> In-Reply-To: <20150901155600.GA8497@nazgul.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit 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 On 09/01/2015 08:56 AM, Borislav Petkov wrote: > On Mon, Aug 31, 2015 at 02:24:08PM -0700, Guenter Roeck wrote: >> That is a matter of driver implementation. Very commonly hwmon drivers >> implement value caching, where data from the device is only read at >> minimum intervals, and the cached values are reported if the information >> is polled too rapidly. > > I don't see how we can use cached values in that case as they'd be > basically a lie as to how much power the CU/processor has consumed. I > guess it would be fairer to the user to warn instead and not issue any > values or to simply delay the read to a min timeout... > This is all a matter of ABI description. I personally don't see the harm in caching values for up to milliseconds and documenting that readings may reflect power consumption from milliseconds ago. However, I don't mind any other solution either if that is considered unacceptable, as long as that solution doesn't break the ABI. Guenter