Messages in this thread Patch in this message | | | From | "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 |
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From: Frederic Weisbecker <fweisbec@gmail.com>
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 <fweisbec@gmail.com> Cc: Alessio Igor Bogani <abogani@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Avi Kivity <avi@redhat.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Christoph Lameter <cl@linux.com> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Kevin Hilman <khilman@ti.com> Cc: Max Krasnyansky <maxk@qualcomm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- 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
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