Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 05/23] nohz: Only enable context tracking on full dynticks CPUs | Date | Thu, 1 Aug 2013 02:31:22 +0200 |
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The context tracking subsystem has the ability to selectively enable the tracking on any defined subset of CPU. This means that we can define a CPU range that doesn't run the context tracking and another range that does.
Now what we want in practice is to enable the tracking on full dynticks CPUs only. In order to perform this, we just need to pass our full dynticks CPU range selection from the full dynticks subsystem to the context tracking.
This way we can spare the overhead of RCU user extended quiescent state and vtime maintainance on the CPUs that are outside the full dynticks range. Just keep in mind the raw context tracking itself is still necessary everywhere.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Kevin Hilman <khilman@linaro.org> --- include/linux/context_tracking.h | 2 ++ kernel/context_tracking.c | 5 +++++ kernel/time/tick-sched.c | 4 ++++ 3 files changed, 11 insertions(+), 0 deletions(-)
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h index d883ff0..1ae37c7 100644 --- a/include/linux/context_tracking.h +++ b/include/linux/context_tracking.h @@ -34,6 +34,8 @@ static inline bool context_tracking_active(void) return __this_cpu_read(context_tracking.active); } +extern void context_tracking_cpu_set(int cpu); + extern void user_enter(void); extern void user_exit(void); diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 7b095de..72bcb25 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -26,6 +26,11 @@ DEFINE_PER_CPU(struct context_tracking, context_tracking) = { #endif }; +void context_tracking_cpu_set(int cpu) +{ + per_cpu(context_tracking.active, cpu) = true; +} + /** * user_enter - Inform the context tracking that the CPU is going to * enter userspace mode. diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index e80183f..6d604fd 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -23,6 +23,7 @@ #include <linux/irq_work.h> #include <linux/posix-timers.h> #include <linux/perf_event.h> +#include <linux/context_tracking.h> #include <asm/irq_regs.h> @@ -350,6 +351,9 @@ void __init tick_nohz_init(void) return; } + for_each_cpu(cpu, nohz_full_mask) + context_tracking_cpu_set(cpu); + cpu_notifier(tick_nohz_cpu_down_callback, 0); cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask); pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf); -- 1.7.5.4
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