Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 14/41] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset | Date | Tue, 1 May 2012 01:54:48 +0200 |
| |
Issue an IPI to restart the tick on a CPU that belongs to a cpuset when its nohz flag gets cleared.
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: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Geoff Levand <geoff@infradead.org> Cc: Gilad Ben Yossef <gilad@benyossef.com> Cc: Hakan Akkan <hakanakkan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@ti.com> Cc: Max Krasnyansky <maxk@qualcomm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.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> --- include/linux/cpuset.h | 2 ++ kernel/cpuset.c | 23 +++++++++++++++++++++++ kernel/time/tick-sched.c | 8 ++++++++ 3 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 5510708..89ef5f3 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -263,6 +263,8 @@ static inline bool cpuset_adaptive_nohz(void) return false; } + +extern void cpuset_exit_nohz_interrupt(void *unused); #else static inline bool cpuset_cpu_adaptive_nohz(int cpu) { return false; } static inline bool cpuset_adaptive_nohz(void) { return false; } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 5a28cf8..00864a0 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1221,6 +1221,14 @@ static void cpuset_change_flag(struct task_struct *tsk, DEFINE_PER_CPU(int, cpu_adaptive_nohz_ref); +static void cpu_exit_nohz(int cpu) +{ + preempt_disable(); + smp_call_function_single(cpu, cpuset_exit_nohz_interrupt, + NULL, true); + preempt_enable(); +} + static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) { int cpu; @@ -1234,6 +1242,21 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) per_cpu(cpu_adaptive_nohz_ref, cpu) += 1; else per_cpu(cpu_adaptive_nohz_ref, cpu) -= 1; + + val = per_cpu(cpu_adaptive_nohz_ref, cpu); + + if (!val) { + /* + * The update to cpu_adaptive_nohz_ref must be + * visible right away. So that once we restart the tick + * from the IPI, it won't be stopped again due to cache + * update lag. + * FIXME: We probably need more to ensure this value is really + * visible right away. + */ + smp_mb(); + cpu_exit_nohz(cpu); + } } } #else diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index fc35d41..fe31add 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -875,6 +875,14 @@ void tick_nohz_check_adaptive(void) } } +void cpuset_exit_nohz_interrupt(void *unused) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + if (ts->tick_stopped && !is_idle_task(current)) + tick_nohz_restart_adaptive(); +} + void tick_nohz_post_schedule(void) { struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); -- 1.7.5.4
| |