sched/isolation: Update nohz documentation to explain tick offload

Update the documentation to reflect the 1Hz tick offload changes.

Signed-off-by: Frederic Weisbecker <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Wanpeng Li <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1d1d53f85ddd79ce2218b7274b3114f41493ac3a..50b9837e985b2a7595fde3cca31627ffee42fb16 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1766,6 +1766,17 @@
 
                        nohz
                          Disable the tick when a single task runs.
+
+                         A residual 1Hz tick is offloaded to workqueues, which you
+                         need to affine to housekeeping through the global
+                         workqueue's affinity configured via the
+                         /sys/devices/virtual/workqueue/cpumask sysfs file, or
+                         by using the 'domain' flag described below.
+
+                         NOTE: by default the global workqueue runs on all CPUs,
+                         so to protect individual CPUs the 'cpumask' file has to
+                         be configured manually after bootup.
+
                        domain
                          Isolate from the general SMP balancing and scheduling
                          algorithms. Note that performing domain isolation this way