Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753903AbbFCGX1 (ORCPT ); Wed, 3 Jun 2015 02:23:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57859 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753826AbbFCGXG (ORCPT ); Wed, 3 Jun 2015 02:23:06 -0400 Date: Wed, 3 Jun 2015 07:37:49 +0100 From: Alexander Gordeev To: linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" Subject: Re: [PATCH 2/2] rcu: Simplify rcu_init_geometry() capacity arithmetics Message-ID: <20150603063748.GD3679@agordeev.usersys.redhat.com> References: <1433312333-23597-2-git-send-email-agordeev@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1433312333-23597-2-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: 2712 Lines: 78 On Wed, Jun 03, 2015 at 08:18:33AM +0200, Alexander Gordeev wrote: > Current code suggests that introducing the extra level to > rcu_capacity[] array makes some of the arithmetic easier. > Well, in fact it appears rather confusing and unnecessary. Please, ignore this one. > Cc: "Paul E. McKenney" > Signed-off-by: Alexander Gordeev > --- > kernel/rcu/tree.c | 16 +++++++--------- > 1 file changed, 7 insertions(+), 9 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 0e8c24d..e6ddd20 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -4038,7 +4038,7 @@ static void __init rcu_init_geometry(void) > { > ulong d; > int i; > - int rcu_capacity[MAX_RCU_LVLS + 1]; > + int rcu_capacity[MAX_RCU_LVLS]; > > /* > * Initialize any unspecified boot parameters. > @@ -4062,12 +4062,10 @@ static void __init rcu_init_geometry(void) > > /* > * Compute number of nodes that can be handled an rcu_node tree > - * with the given number of levels. Setting rcu_capacity[0] makes > - * some of the arithmetic easier. > + * with the given number of levels. > */ > - rcu_capacity[0] = 1; > - rcu_capacity[1] = rcu_fanout_leaf; > - for (i = 2; i <= MAX_RCU_LVLS; i++) > + rcu_capacity[0] = rcu_fanout_leaf; > + for (i = 1; i < MAX_RCU_LVLS; i++) > rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT; > > /* > @@ -4080,7 +4078,7 @@ static void __init rcu_init_geometry(void) > * the rcu_node masks. Complain and fall back to the compile- > * time values if these limits are exceeded. > */ > - if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS]) > + if (nr_cpu_ids > rcu_capacity[MAX_RCU_LVLS - 1]) > panic("rcu_init_geometry: rcu_capacity[] is too small"); > else if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF || > rcu_fanout_leaf > sizeof(unsigned long) * 8) { > @@ -4091,11 +4089,11 @@ static void __init rcu_init_geometry(void) > /* Calculate the number of levels in the tree. */ > for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) { > } > - rcu_num_lvls = i; > + rcu_num_lvls = i + 1; > > /* Calculate the number of rcu_nodes at each level of the tree. */ > for (i = 0; i < rcu_num_lvls; i++) { > - int cap = rcu_capacity[rcu_num_lvls - i]; > + int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; > num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); > } > > -- > 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/