Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751876AbbLNOi7 (ORCPT ); Mon, 14 Dec 2015 09:38:59 -0500 Received: from mail-wm0-f51.google.com ([74.125.82.51]:36403 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751706AbbLNOi5 (ORCPT ); Mon, 14 Dec 2015 09:38:57 -0500 Subject: Re: [RFCv6 PATCH 09/10] sched: deadline: use deadline bandwidth in scale_rt_capacity To: Vincent Guittot References: <1449641971-20827-1-git-send-email-smuckle@linaro.org> <1449641971-20827-10-git-send-email-smuckle@linaro.org> <56697DCB.5050800@unitn.it> <566A7FD2.4050601@unitn.it> Cc: Steve Muckle , Peter Zijlstra , Ingo Molnar , linux-kernel , "linux-pm@vger.kernel.org" , Morten Rasmussen , Dietmar Eggemann , Juri Lelli , Patrick Bellasi , Michael Turquette From: Luca Abeni Message-ID: <566ED47D.6030504@unitn.it> Date: Mon, 14 Dec 2015 15:38:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1962 Lines: 49 On 12/14/2015 03:02 PM, Vincent Guittot wrote: [...] >>>> Small nit: why "average" utilization? I think a better name would be >>>> "runqueue utilization" >>>> or "local utilization", or something similar... If I understand correctly >>>> (sorry if I >>>> missed something), this is not an average, but the sum of the >>>> utilisations >>>> of the tasks >>>> on this runqueue... No? >>> >>> >>> I have used "average" because it doesn't reflect the active/actual >>> utilization of the run-queue but the forecasted average bandwidth of >>> the CPU that will be used by deadline task. >> >> Well, this is just nitpicking, so feel free to ignore (I just mentioned >> this point because I was initially confused by the "average" name). But I >> think this is "maximum", or "worst-case", not "average", because (as far >> as I can understand) this field indicates that SCHED_DEADLINE tasks will >> not be able to consume more than this fraction of CPU (if they try to >> consume more, the scheduler throttles them). >> >>> I'm open to change the name if another one makes more sense >> >> In real-time literature this is often called simply "utilization" (or >> "worst-case >> utilization" by someone): when a task can have a variable execution time, >> its >> utilization is defined as WCET (maximum execution time) / period. > > ok. Let follow real-time literature wording and remove "average" to > keep only utilization. > so the variable will be named: > > s64 util_bw; Well, "utilization" and "bandwidth" are often used to indicate the same quantity, so "util_bw" sounds strange. I'd call it simply "utilization" or "bandwidth" (otherwise, just leave the name as it is... I said this is just nitpicking). Luca -- 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/