linux-kernel - [RFC PATCH 7/8] cgroup/cpuset: Document the new cpuset.cpus.isolation

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Date: Wed, 17 Jan 2024 11:35:10 -0500
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
	Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Neeraj Upadhyay <quic_neeraju@...cinc.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Shuah Khan <shuah@...nel.org>
Cc: cgroups@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	rcu@...r.kernel.org,
	linux-kselftest@...r.kernel.org,
	Mrunal Patel <mpatel@...hat.com>,
	Ryan Phillips <rphillips@...hat.com>,
	Brent Rowsell <browsell@...hat.com>,
	Peter Hunt <pehunt@...hat.com>,
	Cestmir Kalina <ckalina@...hat.com>,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Alex Gladkov <agladkov@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Phil Auld <pauld@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Daniel Bristot de Oliveira <bristot@...nel.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Costa Shulyupin <cshulyup@...hat.com>,
	Waiman Long <longman@...hat.com>
Subject: [RFC PATCH 7/8] cgroup/cpuset: Document the new cpuset.cpus.isolation_full control file

Document the new cpuset.cpus.isolation_full control file. Currently only
the rcu_nocbs flag is supported, but more will be added in the future.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 Documentation/admin-guide/cgroup-v2.rst | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 17e6e9565156..bbd066838f93 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2352,6 +2352,30 @@ Cpuset Interface Files
 	isolated partitions. It will be empty if no isolated partition
 	is created.
 
+  cpuset.cpus.isolation_full
+	A read multiple values and write single value file which exists
+	on root cgroup only.
+
+	This file shows the state of full CPU isolation mode for isolated
+	CPUs in isolated partitions.  It shows either "0' if full CPU
+	isolation mode is disabled, or "1" followed by a comma-separated
+	list of additional CPU isolation flags that are enabled.
+	The currently supported CPU isolation flag is:
+
+	  rcu_nocbs
+		RCU no-callback CPU mode, which prevents such CPUs'
+		callbacks from being invoked in softirq context.
+		Invocation of such CPUs' RCU callbacks will instead be
+		offloaded to "rcuox/N" kthreads created for that purpose.
+		It is similar in functionality to the "rcu_nocbs"
+		boot command line option, but for dynamically created
+		isolated CPUs in isolated partitions.  This flag can
+		only be enabled if such a "rcu_nocbs" option is present
+		in the boot command line of the running kernel.
+
+	Full CPU isolation mode is enabled by writing a non-zero value
+	to this file and disabled by writing a zero value to it.
+
   cpuset.cpus.partition
 	A read-write single value file which exists on non-root
 	cpuset-enabled cgroups.  This flag is owned by the parent cgroup
-- 
2.39.3