Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934283Ab3CMUup (ORCPT ); Wed, 13 Mar 2013 16:50:45 -0400 Received: from relay1.sgi.com ([192.48.179.29]:45057 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933178Ab3CMUun (ORCPT ); Wed, 13 Mar 2013 16:50:43 -0400 Message-ID: <5140E6A1.20107@sgi.com> Date: Wed, 13 Mar 2013 15:50:41 -0500 From: Nathan Zimmer User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: , , , Subject: Re: [PATCH v4 0/2] cpufreq: cpufreq_driver_lock is hot on large systems References: <51265E0F.6090209@sgi.com> <1361550275-5716-1-git-send-email-nzimmer@sgi.com> <3505617.pgqBjPDzlA@vostro.rjw.lan> In-Reply-To: <3505617.pgqBjPDzlA@vostro.rjw.lan> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [128.162.233.145] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1607 Lines: 41 On 03/11/2013 06:23 PM, Rafael J. Wysocki wrote: > On Friday, February 22, 2013 10:24:33 AM Nathan Zimmer wrote: >> I am noticing the cpufreq_driver_lock is quite hot. >> On an idle 512 system perf shows me most of the system time is spent on this >> lock. This is quite significant as top shows 5% of time in system time. >> My solution was to first convert the lock to a rwlock and then to the rcu. >> >> v2: Rebase >> >> v3: Read the RCU documentation instead of skimming it. Also I based on >> git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git pm+acpi-3.9-rc1 >> I assumed that was what you would prefer Rafael. >> >> v4: Removed an unnecessary syncronize_rcu(). >> >> >> Nathan Zimmer (2): >> cpufreq: Convert the cpufreq_driver_lock to a rwlock >> cpufreq: Convert the cpufreq_driver_lock to use the rcu >> >> drivers/cpufreq/cpufreq.c | 286 ++++++++++++++++++++++++++++++++++------------ >> 1 file changed, 211 insertions(+), 75 deletions(-) > I'm going to take patch [1/2] for v3.10, but patch [2/2] still needs some > work it seems. Is that correct? If so, are you going to send an update? > > Rafael > Viresh pointed out that cpufreq_cpu_data still needs a lock. This means placing a vanilla spinlock back into __cpufreq_cpu_get which is what I need to avoid. I haven't had the time I should to sort that out. Nate -- 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/