Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755271Ab2HaXrG (ORCPT ); Fri, 31 Aug 2012 19:47:06 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:60577 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755171Ab2HaXrD (ORCPT ); Fri, 31 Aug 2012 19:47:03 -0400 X-Originating-IP: 217.70.178.145 X-Originating-IP: 173.246.103.110 Date: Fri, 31 Aug 2012 16:46:54 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, 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, sbw@mit.edu, patches@linaro.org, Alessio Igor Bogani , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Kevin Hilman , Max Krasnyansky , Stephen Hemminger , Sven-Thorsten Dietrich Subject: Re: [PATCH tip/core/rcu 06/26] rcu: Ignore userspace extended quiescent state by default Message-ID: <20120831234654.GD11771@jtriplet-mobl1> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346360743-3628-6-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1346360743-3628-6-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2915 Lines: 78 On Thu, Aug 30, 2012 at 02:05:23PM -0700, Paul E. McKenney wrote: > From: Frederic Weisbecker > > By default we don't want to enter into RCU extended quiescent > state while in userspace because doing this produces some overhead > (eg: use of syscall slowpath). Set it off by default and ready to > run when some feature like adaptive tickless need it. > > Signed-off-by: Frederic Weisbecker > Cc: Alessio Igor Bogani > Cc: Andrew Morton > Cc: Avi Kivity > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Geoff Levand > Cc: Gilad Ben Yossef > Cc: Hakan Akkan > Cc: H. Peter Anvin > Cc: Ingo Molnar > Cc: Josh Triplett > Cc: Kevin Hilman > Cc: Max Krasnyansky > Cc: Peter Zijlstra > Cc: Stephen Hemminger > Cc: Steven Rostedt > Cc: Sven-Thorsten Dietrich > Cc: Thomas Gleixner > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > kernel/rcutree.c | 5 ++++- > kernel/rcutree.h | 1 + > 2 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 8bbc7fb..e2fd370 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -210,6 +210,9 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch); > DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { > .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, > .dynticks = ATOMIC_INIT(1), > +#ifdef CONFIG_RCU_USER_QS > + .ignore_user_qs = true, > +#endif > }; > > static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */ > @@ -443,7 +446,7 @@ void rcu_user_enter(void) > > local_irq_save(flags); > rdtp = &__get_cpu_var(rcu_dynticks); > - if (!rdtp->in_user) { > + if (!rdtp->ignore_user_qs && !rdtp->in_user) { > rdtp->in_user = true; > rcu_eqs_enter(1); > } > diff --git a/kernel/rcutree.h b/kernel/rcutree.h > index 0dd5fd6..c190582 100644 > --- a/kernel/rcutree.h > +++ b/kernel/rcutree.h > @@ -103,6 +103,7 @@ struct rcu_dynticks { > int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */ > #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */ > #ifdef CONFIG_RCU_USER_QS > + bool ignore_user_qs; /* Treat userspace as extended QS or not */ > bool in_user; /* Is the CPU in userland from RCU POV? */ > #endif > }; > -- > 1.7.8 > -- 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/