From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753544AbYKZPRe (ORCPT ); Wed, 26 Nov 2008 10:17:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752132AbYKZPR0 (ORCPT ); Wed, 26 Nov 2008 10:17:26 -0500 Received: from viefep18-int.chello.at ([213.46.255.22]:31173 "EHLO viefep18-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751832AbYKZPRZ (ORCPT ); Wed, 26 Nov 2008 10:17:25 -0500 X-SourceIP: 213.46.9.244 Subject: Re: [patch] fix for sched_clock() when using jiffies From: Peter Zijlstra To: Ron Cc: Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: <20081126150645.GA28153@homer.shelbyville.oz> References: <20081126150645.GA28153@homer.shelbyville.oz> Content-Type: text/plain Date: Wed, 26 Nov 2008 16:16:38 +0100 Message-Id: <1227712598.4454.199.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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..d76814e 100644 > --- a/kernel/sched_clock.c > +++ b/kernel/sched_clock.c > @@ -37,7 +37,7 @@ > */ > 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); > } > >