Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754510AbbELWdx (ORCPT ); Tue, 12 May 2015 18:33:53 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:60735 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933967AbbELWbH (ORCPT ); Tue, 12 May 2015 18:31:07 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.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 07/24] rcu: Simplify rcu_init_geometry() capacity arithmetics Date: Tue, 12 May 2015 15:30:37 -0700 Message-Id: <1431469854-3826-7-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1431469854-3826-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150512223034.GA1396@linux.vnet.ibm.com> <1431469854-3826-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051222-0013-0000-0000-00000AB42534 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2557 Lines: 73 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" Signed-off-by: Alexander Gordeev Signed-off-by: Paul E. McKenney --- 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 d37a7f80ad9c..2473a60161a3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4052,7 +4052,7 @@ 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. @@ -4076,12 +4076,10 @@ 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; /* @@ -4094,7 +4092,7 @@ 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) { @@ -4105,11 +4103,11 @@ static void __init rcu_init_geometry(void) /* Calculate the number of levels in the tree. */ 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 -- 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/