From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934204AbbELW6g (ORCPT ); Tue, 12 May 2015 18:58:36 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:57376 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933968AbbELW6W (ORCPT ); Tue, 12 May 2015 18:58:22 -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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/13] rcutorture: Allow negative values of nreaders to oversubscribe Date: Tue, 12 May 2015 15:58:04 -0700 Message-Id: <1431471493-5431-4-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1431471493-5431-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150512225753.GA5012@linux.vnet.ibm.com> <1431471493-5431-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051222-8236-0000-0000-00000B6F27CB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" By default, with rcutorture.nreaders equal to -1, rcutorture provisions N-1 reader kthreads, where N is the number of CPUs. This avoids rcutorture-induced stalls, but also avoids heavier levels of torture. This commit therefore allows negative values of rcutorture.nreaders to specify larger numbers of reader kthreads, so that for example rcutorture.nreaders=-2 provisions N kthreads and rcutorture.nreaders=-5 provisions N+3 kthreads. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index a67ef6ff86b0..7294d605c481 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1701,7 +1701,7 @@ rcu_torture_init(void) if (nreaders >= 0) { nrealreaders = nreaders; } else { - nrealreaders = num_online_cpus() - 1; + nrealreaders = num_online_cpus() - 2 - nreaders; if (nrealreaders <= 0) nrealreaders = 1; } -- 1.8.1.5