From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753570AbYK1Oky (ORCPT ); Fri, 28 Nov 2008 09:40:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752082AbYK1Okq (ORCPT ); Fri, 28 Nov 2008 09:40:46 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:54498 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751996AbYK1Okp (ORCPT ); Fri, 28 Nov 2008 09:40:45 -0500 Date: Fri, 28 Nov 2008 15:40:39 +0100 From: Ingo Molnar To: Ron Cc: Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [patch] fix for sched_clock() when using jiffies Message-ID: <20081128144039.GG28138@elte.hu> References: <20081126150645.GA28153@homer.shelbyville.oz> <1227712598.4454.199.camel@twins> <20081126153152.GB28153@homer.shelbyville.oz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081126153152.GB28153@homer.shelbyville.oz> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ron wrote: > On Wed, Nov 26, 2008 at 04:16:38PM +0100, Peter Zijlstra wrote: > > On Thu, 2008-11-27 at 01:36 +1030, Ron wrote: > > > Hi, > > > > > > I'm in the process of updating a port for an ARM based chip we've been > > > working on, from 2.6.22-rc4'ish to the current HEAD of Linus' tree, and > > > I started seeing the following: > > > > > > [ 0.000000] PID hash table entries: 512 (order: 9, 2048 bytes) > > > [42949372.970000] Dentry cache hash table entries: 16384 (order: 4, 65536 bytes) > > > > > > The reason appears to be that printk_clock() has been replaced with a > > > call to cpu_clock, which in our case currently falls back to the default > > > (weak) implementation of sched_clock() that uses jiffies -- but doesn't > > > account for the initial offset of the jiffy count. The following simple > > > patch fixes it for me, in line with what printk_clock used to do. > > > > > > > Looks good, except I suspect this line will now be longer than 80 > > characters and you forgot to provide your signed-off-by line. > > diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c > index 8178724..1ce2e53 100644 > --- a/kernel/sched_clock.c > +++ b/kernel/sched_clock.c > @@ -37,7 +37,8 @@ > */ > unsigned long long __attribute__((weak)) sched_clock(void) > { > - return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); > + return (unsigned long long)(jiffies - INITIAL_JIFFIES) > + * (NSEC_PER_SEC / HZ); > } > > static __read_mostly int sched_clock_running; > > > Signed-off-by: Ron Lee whitespace damage: all tabs are space. please see Documentation/email-clients.txt for how to send patches. Also, when you resend a patch, do it without quotes and by including the fill commit log again - to make it easier to apply it. (and not forcing me to cut&paste various emails - it's fundamentall error-prone) Ingo