Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761749Ab0GTV5I (ORCPT ); Tue, 20 Jul 2010 17:57:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:5876 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761675Ab0GTV5G (ORCPT ); Tue, 20 Jul 2010 17:57:06 -0400 Message-ID: <4C461BAF.90804@redhat.com> Date: Tue, 20 Jul 2010 11:57:03 -1000 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Avi Kivity CC: KVM , Marcelo Tosatti , Glauber Costa , Linux-kernel Subject: Re: [PATCH 04/18] Make cpu_tsc_khz updates use local CPU References: <1278987938-23873-1-git-send-email-zamsden@redhat.com> <1278987938-23873-5-git-send-email-zamsden@redhat.com> <4C431374.2020804@redhat.com> <4C44B035.7080604@redhat.com> <4C456422.7030708@redhat.com> In-Reply-To: <4C456422.7030708@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1395 Lines: 40 On 07/19/2010 10:53 PM, Avi Kivity wrote: > On 07/19/2010 11:06 PM, Zachary Amsden wrote: >>>> +static void tsc_khz_changed(void *data) >>>> { >>>> - /* nothing */ >>>> + struct cpufreq_freqs *freq = data; >>>> + unsigned long khz = 0; >>>> + >>>> + if (data) >>>> + khz = freq->new; >>>> + else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) >>>> + khz = cpufreq_quick_get(raw_smp_processor_id()); >>>> + if (!khz) >>>> + khz = tsc_khz; >>>> + __get_cpu_var(cpu_tsc_khz) = khz; >>>> } >>> >>> Do we really need to cache cpufreq_quick_get()? If it's really >>> quick, why not just use it everywhere instead of cacheing it? Not a >>> comment on this patch. >>> >> >> >> If cpufreq is compiled in, but disabled, it returns zero, so we need >> some sort of logic. > > Maybe it's better to put it into cpufreq_quick_get(). Inconsistent > APIs that appear to work are bad. > I don't think it's quite so simple; cpufreq is platform independent and tsc_khz is a platform specific export. It seems cpufreq is designed to return zero when disabled and we're the unusual ones for wanting to use it. Zach -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/