From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754795AbbGQWbV (ORCPT ); Fri, 17 Jul 2015 18:31:21 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:44233 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753112AbbGQWbL (ORCPT ); Fri, 17 Jul 2015 18:31:11 -0400 X-Helo: d03dlp01.boulder.ibm.com X-MailFrom: paulmck@linux.vnet.ibm.com X-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Alexander Gordeev , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 05/12] rcu: Simplify rcu_init_geometry() capacity arithmetics Date: Fri, 17 Jul 2015 15:30:56 -0700 Message-Id: <1437172263-15466-5-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1437172263-15466-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150717223041.GA14464@linux.vnet.ibm.com> <1437172263-15466-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15071722-0009-0000-0000-00000C91398A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexander Gordeev 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. Cc: "Paul E. McKenney" Cc: Steven Rostedt Signed-off-by: Alexander Gordeev Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 37ca8a867a1c..2103beedb49f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4082,7 +4082,7 @@ 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. @@ -4119,29 +4119,27 @@ 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] * RCU_FANOUT; /* * The tree must be able to accommodate the configured number of CPUs. * If this limit is exceeded than we have a serious problem elsewhere. */ - 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"); /* Calculate the number of levels in the tree. */ - for (i = 1; nr_cpu_ids > rcu_capacity[i]; i++) { + for (i = 0; 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); } -- 1.8.1.5