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: Mon, 10 Jun 2013 15:39:05 -0700 Message-ID: <51B65589.5030700@hp.com> References: <51B0CADF.8040508@hp.com> <51B3F4A3.3020502@gmail.com> <51B63847.1010008@hp.com> <51B652F9.4020402@hp.com> <51B65430.8050501@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from g1t0029.austin.hp.com ([15.216.28.36]:20057 "EHLO g1t0029.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751929Ab3FJWjH (ORCPT ); Mon, 10 Jun 2013 18:39:07 -0400 In-Reply-To: <51B65430.8050501@gmail.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 03:33 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 :) happy benchmarking, rick jones Interestingly enough, on the old Centrino-based laptop where I've tried it (on AC power), read_hpet has gone away completely. I'd noticed that was visible in several examples in the tutorial on the wiki, but it wasn't explained.