Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753845AbbFCGXI (ORCPT ); Wed, 3 Jun 2015 02:23:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43343 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753137AbbFCGWq (ORCPT ); Wed, 3 Jun 2015 02:22:46 -0400 Date: Wed, 3 Jun 2015 07:37:29 +0100 From: Alexander Gordeev To: linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" Subject: Re: [PATCH 1/2] rcu: Cleanup rcu_init_geometry() code and arithmetics Message-ID: <20150603063728.GC3679@agordeev.usersys.redhat.com> References: <1433312333-23597-1-git-send-email-agordeev@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1433312333-23597-1-git-send-email-agordeev@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2319 Lines: 78 On Wed, Jun 03, 2015 at 08:18:32AM +0200, Alexander Gordeev wrote: > This update simplifies rcu_init_geometry() code flow > and makes calculation of the total number of rcu_node > structures more easy to read. > > The update relies on the fact num_rcu_lvl[] is never > accessed beyond rcu_num_lvls index by the rest of the > code. Therefore, there is no need initialize the whole > num_rcu_lvl[]. Please, ignore this one. > Cc: "Paul E. McKenney" > Signed-off-by: Alexander Gordeev > --- > kernel/rcu/tree.c | 24 ++++++++++-------------- > 1 file changed, 10 insertions(+), 14 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index d77b0fb..0e8c24d 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -4038,7 +4038,6 @@ static void __init rcu_init_geometry(void) > { > ulong d; > int i; > - int j; > int rcu_capacity[MAX_RCU_LVLS + 1]; > > /* > @@ -4089,24 +4088,21 @@ static void __init rcu_init_geometry(void) > return; > } > > + /* Calculate the number of levels in the tree. */ > + for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) { > + } > + rcu_num_lvls = i; > + > /* Calculate the number of rcu_nodes at each level of the tree. */ > - for (i = 1; i <= MAX_RCU_LVLS; i++) > - if (nr_cpu_ids <= rcu_capacity[i]) { > - for (j = 0; j <= i; j++) { > - int cap = rcu_capacity[i - j]; > - num_rcu_lvl[j] = DIV_ROUND_UP(nr_cpu_ids, cap); > - } > - rcu_num_lvls = i; > - for (j = i + 1; j <= MAX_RCU_LVLS; j++) > - num_rcu_lvl[j] = 0; > - break; > - } > + for (i = 0; i < rcu_num_lvls; i++) { > + int cap = rcu_capacity[rcu_num_lvls - i]; > + num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); > + } > > /* Calculate the total number of rcu_node structures. */ > rcu_num_nodes = 0; > - for (i = 0; i <= MAX_RCU_LVLS; i++) > + for (i = 0; i < rcu_num_lvls; i++) > rcu_num_nodes += num_rcu_lvl[i]; > - rcu_num_nodes -= nr_cpu_ids; > } > > void __init rcu_init(void) > -- > 1.8.3.1 > -- Regards, Alexander Gordeev agordeev@redhat.com -- 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/