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author | Frederic Weisbecker <fweisbec@gmail.com> | 2012-12-18 17:32:19 +0100 |
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committer | Frederic Weisbecker <fweisbec@gmail.com> | 2013-03-21 15:38:33 +0100 |
commit | a831881be220358a1d28c5d95d69449fb6d623ca (patch) | |
tree | 769ab069e2837a9bd3613046110468cd87c8c3fa /kernel/time/Kconfig | |
parent | a8d7ad52a7befbde896276d05c75c90fed48b5bf (diff) | |
download | linux-a831881be220358a1d28c5d95d69449fb6d623ca.tar.gz linux-a831881be220358a1d28c5d95d69449fb6d623ca.tar.bz2 linux-a831881be220358a1d28c5d95d69449fb6d623ca.zip |
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 'kernel/time/Kconfig')
-rw-r--r-- | kernel/time/Kconfig | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 24510d84efd7..5a87c03e45ad 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -79,6 +79,25 @@ config NO_HZ only trigger on an as-needed basis both when the system is busy and when the system is idle. +config NO_HZ_EXTENDED + bool "Full dynticks system" + depends on NO_HZ && RCU_USER_QS && VIRT_CPU_ACCOUNTING_GEN && RCU_NOCB_CPU && SMP + select CONTEXT_TRACKING_FORCE + help + Adaptively try to shutdown the tick whenever possible, even when + the CPU is running tasks. Typically this requires running a single + task on the CPU. Chances for running tickless are maximized when + the task mostly runs in userspace and has few kernel activity. + + You need to fill up the nohz_extended boot parameter with the + desired range of dynticks CPUs. + + This is implemented at the expense of some overhead in user <-> kernel + transitions: syscalls, exceptions and interrupts. Even when it's + dynamically off. + + Say N. + config HIGH_RES_TIMERS bool "High Resolution Timer Support" depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS |