From patchwork Wed Feb 1 19:41:35 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 6534 Return-Path: X-Original-To: patchwork@peony.canonical.com Delivered-To: patchwork@peony.canonical.com Received: from fiordland.canonical.com (fiordland.canonical.com [91.189.94.145]) by peony.canonical.com (Postfix) with ESMTP id C213323E81 for ; Wed, 1 Feb 2012 19:43:30 +0000 (UTC) Received: from mail-bk0-f52.google.com (mail-bk0-f52.google.com [209.85.214.52]) by fiordland.canonical.com (Postfix) with ESMTP id B02D4A1834C for ; Wed, 1 Feb 2012 19:43:30 +0000 (UTC) Received: by mail-bk0-f52.google.com with SMTP id r19so1858856bka.11 for ; Wed, 01 Feb 2012 11:43:30 -0800 (PST) Received: by 10.204.9.198 with SMTP id m6mr6795671bkm.74.1328125410522; Wed, 01 Feb 2012 11:43:30 -0800 (PST) X-Forwarded-To: linaro-patchwork@canonical.com X-Forwarded-For: patch@linaro.org linaro-patchwork@canonical.com Delivered-To: patches@linaro.org Received: by 10.204.130.220 with SMTP id u28cs220032bks; Wed, 1 Feb 2012 11:43:30 -0800 (PST) Received: by 10.68.239.230 with SMTP id vv6mr247940pbc.94.1328125408370; Wed, 01 Feb 2012 11:43:28 -0800 (PST) Received: from e33.co.us.ibm.com (e33.co.us.ibm.com. [32.97.110.151]) by mx.google.com with ESMTPS id b4si247992pbd.55.2012.02.01.11.43.27 (version=TLSv1/SSLv3 cipher=OTHER); Wed, 01 Feb 2012 11:43:28 -0800 (PST) Received-SPF: pass (google.com: domain of paulmck@linux.vnet.ibm.com designates 32.97.110.151 as permitted sender) client-ip=32.97.110.151; Authentication-Results: mx.google.com; spf=pass (google.com: domain of paulmck@linux.vnet.ibm.com designates 32.97.110.151 as permitted sender) smtp.mail=paulmck@linux.vnet.ibm.com Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 Feb 2012 12:43:26 -0700 Received: from d03dlp01.boulder.ibm.com (9.17.202.177) by e33.co.us.ibm.com (192.168.1.133) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 1 Feb 2012 12:42:32 -0700 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 3BAAB1FF004F for ; Wed, 1 Feb 2012 12:42:31 -0700 (MST) Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q11JgNA2170886 for ; Wed, 1 Feb 2012 12:42:25 -0700 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q11JgAsV032398 for ; Wed, 1 Feb 2012 12:42:13 -0700 Received: from paulmck-ThinkPad-W500 ([9.47.24.98]) by d03av01.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id q11Jg7He031730; Wed, 1 Feb 2012 12:42:07 -0700 Received: by paulmck-ThinkPad-W500 (Postfix, from userid 1000) id 6EA24E5200; Wed, 1 Feb 2012 11:42:03 -0800 (PST) From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 17/41] rcu: Remove single-rcu_node optimization in rcu_start_gp() Date: Wed, 1 Feb 2012 11:41:35 -0800 Message-Id: <1328125319-5205-17-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120201194131.GA10028@linux.vnet.ibm.com> <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020119-2398-0000-0000-000003DD0E2C From: "Paul E. McKenney" The grace-period initialization sequence in rcu_start_gp() has a special case for systems where the rcu_node tree is a single rcu_node structure. This made sense some years ago when systems were smaller and up to 64 CPUs could share a single rcu_node structure, but now that large systems are common and a given leaf rcu_node structure can support only 16 CPUs (due to lock contention on the rcu_node's ->lock field), this optimization is almost never taken. And even the small mobile platforms that might make use of it might rather have the kernel text reduction. Therefore, this commit removes the check for single-rcu_node trees. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcutree.c | 18 ------------------ 1 files changed, 0 insertions(+), 18 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index ee2009d..38d143b 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -984,26 +984,8 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags) rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; record_gp_stall_check_time(rsp); - - /* Special-case the common single-level case. */ - if (NUM_RCU_NODES == 1) { - rcu_preempt_check_blocked_tasks(rnp); - rnp->qsmask = rnp->qsmaskinit; - rnp->gpnum = rsp->gpnum; - rnp->completed = rsp->completed; - rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state OK */ - rcu_start_gp_per_cpu(rsp, rnp, rdp); - rcu_preempt_boost_start_gp(rnp); - trace_rcu_grace_period_init(rsp->name, rnp->gpnum, - rnp->level, rnp->grplo, - rnp->grphi, rnp->qsmask); - raw_spin_unlock_irqrestore(&rnp->lock, flags); - return; - } - raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ - /* Exclude any concurrent CPU-hotplug operations. */ raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */