From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: measuring and/or dealing with "idleness" and variable frequency Date: Wed, 12 Jun 2013 14:21:30 -0700 Message-ID: <51B8E65A.7090102@hp.com> References: <51B0CADF.8040508@hp.com> <51B3F4A3.3020502@gmail.com> <51B63847.1010008@hp.com> <51B652F9.4020402@hp.com> <51B65430.8050501@gmail.com> <51B65589.5030700@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from g1t0027.austin.hp.com ([15.216.28.34]:13217 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755908Ab3FLVVb (ORCPT ); Wed, 12 Jun 2013 17:21:31 -0400 In-Reply-To: <51B65589.5030700@hp.com> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: David Ahern Cc: linux-perf-users@vger.kernel.org On 06/10/2013 03:39 PM, Rick Jones wrote: > On 06/10/2013 03:33 PM, David Ahern wrote: >> On 6/10/13 4:28 PM, Rick Jones wrote: >>>> I think I could get what I want from that - assuming I could get >>>> that to >>>> a kernel I can use in my test env, but am guessing it is rather more >>>> than I"m looking for at the moment. I'm wondering if there might be a >>>> simpler way to go - just get the idle loop to keep looping rather than >>>> halt (?) the thread, so there would still be cycle events in the PMU? >>>> (And perhaps set the system to a static, high-performance mode to avoid >>>> frequency changes and maybe even disable HT?) >>> >>> Or, after having found >>> https://www.kernel.org/doc/Documentation/kernel-parameters.txt, perhaps >>> idle=poll? >> >> Yes, that should turn the server into a power-sucking space heater and >> keep the cycles counter firing. > > Excellent - I can live with the server being a power-sucking space > heater for the duration of my profiling. Heck, many of the servers I > used to work on were always power-sucking space heaters :) Just for the archives and anyone looking to go "space heater" in the future - it is a Good Idea (tm) to disable hyper threads (at least with this sort of hyper threading in E5-2670 processors) or you can have what I presume are two HT's battling one another in the idle loop. rick jones