From a831881be220358a1d28c5d95d69449fb6d623ca Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Tue, 18 Dec 2012 17:32:19 +0100 Subject: 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 Signed-off-by: Frederic Weisbecker Cc: Andrew Morton Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Li Zhong Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- Documentation/kernel-parameters.txt | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation') 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 -- cgit v1.2.3