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authorFrederic Weisbecker <fweisbec@gmail.com>2012-12-18 20:32:19 +0400
committerFrederic Weisbecker <fweisbec@gmail.com>2013-03-21 18:38:33 +0400
commita831881be220358a1d28c5d95d69449fb6d623ca (patch)
tree769ab069e2837a9bd3613046110468cd87c8c3fa /include/linux/tick.h
parenta8d7ad52a7befbde896276d05c75c90fed48b5bf (diff)
downloadlinux-a831881be220358a1d28c5d95d69449fb6d623ca.tar.xz
nohz: Basic full dynticks interface
For extreme usecases such as Real Time or HPC, having the ability to shutdown the tick when a single task runs on a CPU is a desired feature: * Reducing the amount of interrupts improves throughput for CPU-bound tasks. The CPU is less distracted from its real job, from an execution time and from the cache point of views. * This also improve latency response as we have less critical sections. Start with introducing a very simple interface to define full dynticks CPU: use a boot time option defined cpumask through the "nohz_extended=" kernel parameter. CPUs that are part of this range will have their tick shutdown whenever possible: provided they run a single task and they don't do kernel activity that require the periodic tick. These details will be later documented in Documentation/* An online CPU must be kept outside this range to handle the timekeeping. Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> 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: Ingo Molnar <mingo@kernel.org> Cc: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Namhyung Kim <namhyung.kim@lge.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/tick.h')
-rw-r--r--include/linux/tick.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 553272e6af55..44bfa8aa439f 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -157,6 +157,13 @@ static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }
static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
# endif /* !NO_HZ */
+#ifdef CONFIG_NO_HZ_EXTENDED
+extern int tick_nohz_extended_cpu(int cpu);
+#else
+static inline int tick_nohz_extended_cpu(int cpu) { return 0; }
+#endif
+
+
# ifdef CONFIG_CPU_IDLE_GOV_MENU
extern void menu_hrtimer_cancel(void);
# else