From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758280AbYE0Qme (ORCPT ); Tue, 27 May 2008 12:42:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755718AbYE0Qm1 (ORCPT ); Tue, 27 May 2008 12:42:27 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:37324 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754638AbYE0Qm0 (ORCPT ); Tue, 27 May 2008 12:42:26 -0400 Date: Tue, 27 May 2008 09:40:35 -0700 From: Arjan van de Ven To: svaidy@linux.vnet.ibm.com Cc: Linux Kernel , venkatesh.pallipadi@intel.com, suresh.b.siddha@intel.com, Michael Neuling , Balbir Singh , "Amit K. Arora" Subject: Re: [RFC PATCH v1 0/3] Scaled statistics using APERF/MPERF in x86 Message-ID: <20080527094035.67ccda32@infradead.org> In-Reply-To: <20080527140440.GD5181@dirshya.in.ibm.com> References: <20080526142513.24680.97164.stgit@drishya.in.ibm.com> <20080526085000.33787eac@infradead.org> <20080527140440.GD5181@dirshya.in.ibm.com> Organization: Intel X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.9; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 May 2008 19:34:40 +0530 Vaidyanathan Srinivasan wrote: > > What we are proposing is a scaled time value that is scaled to the > current CPU capacity. If the scaled utilisation is 50% when the CPU > is at 100% capacity, it is expected to remain at 50% even if the CPU's > capacity is dropped to 50%, while the traditional utilisation value > will be 100%. When you use the word "capacity" I cringe ;( > > The problem in the above two cases is that we had assumed that the > maximum CPU capacity is 100% at normal capacity (without IDA). > > If the CPU is at half the maximum frequency, then scaled stats should > show 50%. see frequency != capacity. It's about more than frequency. It's about how much cache you have available too. If you run single threaded on a dual core cpu, you have 100% of the cache, but the cpu is 50% idle. But that doesn't mean that when you double the load, you actually get 2x the performance. So you're not at 50% of capacity! > The point I am trying to make is whether scaling should be done > relative to CPUs designed maximum capacity or maximum capacity under > current constraints is to be discussed. now you're back at "capacity".. we were at frequency before ;( > > Case A: > ------ > > Scaled stats is stats relative to maximum designed capacity including > IDA you don't know what that is though.