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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 /Documentation/kernel-parameters.txt
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 'Documentation/kernel-parameters.txt')
-rw-r--r--Documentation/kernel-parameters.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..231698feaddc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1913,6 +1913,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Valid arguments: on, off
Default: on
+ nohz_extended= [KNL,BOOT]
+ In kernels built with CONFIG_NO_HZ_EXTENDED=y, set
+ the specified list of CPUs whose tick will be stopped
+ whenever possible. You need to keep at least one online
+ CPU outside the range to maintain the timekeeping.
+
noiotrap [SH] Disables trapped I/O port accesses.
noirqdebug [X86-32] Disables the code which attempts to detect and