From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751401AbdAWS5C (ORCPT ); Mon, 23 Jan 2017 13:57:02 -0500 Received: from mga05.intel.com ([192.55.52.43]:38809 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750948AbdAWS5B (ORCPT ); Mon, 23 Jan 2017 13:57:01 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.33,275,1477983600"; d="scan'208";a="57264588" Date: Mon, 23 Jan 2017 10:57:26 -0800 (PST) From: Shivappa Vikas X-X-Sender: vikas@vshiva-Udesk To: Thomas Gleixner cc: Shivappa Vikas , Vikas Shivappa , linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, ravi.v.shankar@intel.com, tony.luck@intel.com, fenghua.yu@intel.com, h.peter.anvin@intel.com Subject: Re: [PATCH 1/8] Documentation, x86: Documentation for Intel Mem b/w allocation user interface In-Reply-To: Message-ID: References: <1484076788-25385-1-git-send-email-vikas.shivappa@linux.intel.com> <1484076788-25385-2-git-send-email-vikas.shivappa@linux.intel.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 18 Jan 2017, Thomas Gleixner wrote: > On Tue, 17 Jan 2017, Shivappa Vikas wrote: >> On Mon, 16 Jan 2017, Thomas Gleixner wrote: >>> This interface is really crap. The natural way to express it is: >>> >>> Requested Bandwidth = X % >> >> I wanted to do it this way which did seem more intuitive but the issue is with >> the non-linear scale which the hardware does not guarantee a particular >> percentage for a particular value. Or we don't know the curve for delay value >> vs. actual b/w throttled. >> >> ex: in non linear scale , the granularity is 2^n. >> Max : 512 >> >> Say a value of 256 is not guaranteed to have 50% or even follow a curve where >> we can calculate the corresponding percentage. > > The question is whether this non linear scale thing is just a first > implementation attempt and any sane hardware in the future will use the > percentage value (which is an approximation as well). > > If that non-linear scale is not going to be prevalent, then we really can > live with the fallout of a particular CPU type. > > If it's going to stay, then Intel should be able to provide simple tables > which give us the required information for a particular CPU model. By sample table - does this mean we can map a throttle value in non-linear scale to its percentage ? Thanks, Vikas > > Thanks, > > tglx >