From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758263Ab2GKS1K (ORCPT ); Wed, 11 Jul 2012 14:27:10 -0400 Received: from mail-yx0-f174.google.com ([209.85.213.174]:65226 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758249Ab2GKS1F (ORCPT ); Wed, 11 Jul 2012 14:27:05 -0400 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: LKML , Frederic Weisbecker , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Josh Triplett , Kevin Hilman , Max Krasnyansky , Peter Zijlstra , Stephen Hemminger , Steven Rostedt , Sven-Thorsten Dietrich , Thomas Gleixner Subject: [PATCH 03/11] rcu: Ignore userspace extended quiescent state by default Date: Wed, 11 Jul 2012 20:26:32 +0200 Message-Id: <1342031200-22731-4-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1342031200-22731-1-git-send-email-fweisbec@gmail.com> References: <1342031200-22731-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 d5df618..78b0c30 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -209,6 +209,9 @@ 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. */ @@ -442,7 +445,7 @@ 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 4d82cb5..55bcef1 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 }; -- 1.7.5.4