linux-kernel - [PATCH 5/5] sched/isolation: Document "nohz

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Date:   Tue, 19 Dec 2017 04:23:58 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Chris Metcalf <cmetcalf@...lanox.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Luiz Capitulino <lcapitulino@...hat.com>,
        Christoph Lameter <cl@...ux.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Wanpeng Li <kernellwp@...il.com>,
        Mike Galbraith <efault@....de>, Rik van Riel <riel@...hat.com>
Subject: [PATCH 5/5] sched/isolation: Document "nohz_offload" flag

Document the interface to offload the 1Hz scheduler tick in full
dynticks mode. Also improve the comment about the existing "nohz" flag
in order to differentiate its behaviour.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Chris Metcalf <cmetcalf@...lanox.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Luiz Capitulino <lcapitulino@...hat.com>
Cc: Mike Galbraith <efault@....de>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Wanpeng Li <kernellwp@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
---
 Documentation/admin-guide/kernel-parameters.txt | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 1683107..fcc5fd9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1745,7 +1745,12 @@
 			specified in the flag list (default: domain):
 
 			nohz
-			  Disable the tick when a single task runs.
+			  Disable the tick when a single task runs. A residual 1Hz
+			  tick remains to maintain scheduler stats alive.
+			nohz_offload
+			  Like nohz but the residual 1Hz tick is offloaded to
+			  housekeeping CPUs, leaving the CPU free of any tick if
+			  nothing else requests it.
 			domain
 			  Isolate from the general SMP balancing and scheduling
 			  algorithms. Note that performing domain isolation this way
-- 
2.7.4