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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, 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 , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 06/26] rcu: Ignore userspace extended quiescent state by default Date: Thu, 30 Aug 2012 14:05:23 -0700 Message-Id: <1346360743-3628-6-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083021-7408-0000-0000-0000080B568C X-Gm-Message-State: ALoCoQnJq8+323xs5nmY1JO4W55N7jtAV+Q9F8TZ77akD1eFALzuJl3gxT6A2nT3cIPR0ym4XHL3 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 };