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| author | Frederic Weisbecker <fweisbec@gmail.com> | 2012-12-18 20:32:19 +0400 |
|---|---|---|
| committer | Frederic Weisbecker <fweisbec@gmail.com> | 2013-03-21 18:38:33 +0400 |
| commit | a831881be220358a1d28c5d95d69449fb6d623ca (patch) | |
| tree | 769ab069e2837a9bd3613046110468cd87c8c3fa /include/linux/tick.h | |
| parent | a8d7ad52a7befbde896276d05c75c90fed48b5bf (diff) | |
| download | linux-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.h | 7 |
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 |