Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757619Ab3ENRuZ (ORCPT ); Tue, 14 May 2013 13:50:25 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:53231 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754703Ab3ENRuY (ORCPT ); Tue, 14 May 2013 13:50:24 -0400 Date: Tue, 14 May 2013 10:49:33 -0700 From: "Paul E. McKenney" To: Joerg Roedel Cc: =?iso-8859-1?Q?Bj=F8rn?= Mork , "Paul E. McKenney" , linux-kernel@vger.kernel.org Subject: Re: Bisected post-3.9 regression: Resume takes 5 times as much time as with v3.9 Message-ID: <20130514174933.GF4442@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <87r4hdjsu5.fsf@nemi.mork.no> <20130512113157.GG3648@linux.vnet.ibm.com> <20130512182935.GD24440@8bytes.org> <20130512205747.GK3648@linux.vnet.ibm.com> <20130512213430.GE24440@8bytes.org> <20130513013518.GM3648@linux.vnet.ibm.com> <20130513140005.GA9165@linux.vnet.ibm.com> <20130514173739.GH24440@8bytes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20130514173739.GH24440@8bytes.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13051417-5406-0000-0000-0000087663CB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2087 Lines: 57 On Tue, May 14, 2013 at 07:37:39PM +0200, Joerg Roedel wrote: > Hi Paul, > > On Mon, May 13, 2013 at 07:00:05AM -0700, Paul E. McKenney wrote: > > rcu: Fix comparison sense in rcu_needs_cpu() > > > > Commit c0f4dfd4f (rcu: Make RCU_FAST_NO_HZ take advantage of numbered > > callbacks) introduced a bug that can result in excessively long grace > > periods. This bug reverse the senes of the "if" statement checking > > for lazy callbacks, so that RCU takes a lazy approach when there are > > in fact non-lazy callbacks. This can result in excessive boot, suspend, > > and resume times. > > > > This commit therefore fixes the sense of this "if" statement. > > > > Reported-by: Borislav Petkov > > Reported-by: Bj?rn Mork > > Reported-by: Joerg Roedel > > Signed-off-by: Paul E. McKenney > > Just tested the patch, it fixes the long boot delay for me. Thanks for > fixing this. Thank you Joerg!!! Thanx, Paul > Tested-by: Joerg Roedel > > > > > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > > index 641991d..63098a5 100644 > > --- a/kernel/rcutree_plugin.h > > +++ b/kernel/rcutree_plugin.h > > @@ -1692,7 +1692,7 @@ int rcu_needs_cpu(int cpu, unsigned long *dj) > > rdtp->last_accelerate = jiffies; > > > > /* Request timer delay depending on laziness, and round. */ > > - if (rdtp->all_lazy) { > > + if (!rdtp->all_lazy) { > > *dj = round_up(rcu_idle_gp_delay + jiffies, > > rcu_idle_gp_delay) - jiffies; > > } else { > > > > -- > 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/ > -- 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/