From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932163AbcHWEIM (ORCPT ); Tue, 23 Aug 2016 00:08:12 -0400 Received: from mga04.intel.com ([192.55.52.120]:46305 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750988AbcHWEIK (ORCPT ); Tue, 23 Aug 2016 00:08:10 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,564,1464678000"; d="scan'208";a="1045680253" Message-ID: <1471925285.5747.5.camel@linux.intel.com> Subject: Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection algorithm for Core From: Srinivas Pandruvada To: Wanpeng Li , "Rafael J. Wysocki" Cc: Linux PM list , Peter Zijlstra , Viresh Kumar , Linux Kernel Mailing List , Steve Muckle , Juri Lelli , Ingo Molnar Date: Mon, 22 Aug 2016 21:08:05 -0700 In-Reply-To: References: <3752826.3sXAQIvcIA@vostro.rjw.lan> <1572483.RZjvRFdxPx@vostro.rjw.lan> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.4 (3.20.4-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2016-08-23 at 11:48 +0800, Wanpeng Li wrote: > Hi Rafael, > 2016-08-01 7:38 GMT+08:00 Rafael J. Wysocki : > > > > From: Rafael J. Wysocki > > > > The PID-base P-state selection algorithm used by intel_pstate for > > Core processors is based on very weak foundations.  Namely, its > > decisions are mostly based on the values of the APERF and MPERF > > feedback registers and it only estimates the actual utilization to > > check if it is not extremely low (in order to avoid getting stuck > > in the highest P-state in that case). > > > > Since it generally causes the CPU P-state to ramp up quickly, it > > leads to satisfactory performance, but the metric used by it is > > only > > really valid when the CPU changes P-states by itself (ie. in the > > turbo > > range) and if the P-state value set by the driver is treated by the > > CPU as the upper limit on turbo P-states selected by it. > > Do you mean CPU will ignore the request value which is submitted by > intel_pstate driver in the turbo range, but respect the upper limit > on > the turbo P-states which is submitted by intel_pstate driver? Any request to request a P-state even upper limit can be totally ignored in turbo range.  Thanks, Srinivas > > Regards, > Wanpeng Li > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html