cgroup: document cgroup_no_v1=

Add cgroup_no_v1= to kernel-parameters.txt, and a small blurb to
cgroup-v2.txt section about transitioning from cgroup to cgroup2.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
index 9ae148ab12559fcf1621a5fb66042ad020d98606..3922ae1654fd40b297d045f1b7f6fcae0a8e6924 100644 (file)
--- a/Documentation/cgroup-v2.txt
+++ b/Documentation/cgroup-v2.txt
@@ -132,6 +132,12 @@ strongly discouraged for production use.  It is recommended to decide
 the hierarchies and controller associations before starting using the
 controllers after system boot.
 
+During transition to v2, system management software might still
+automount the v1 cgroup filesystem and so hijack all controllers
+during boot, before manual intervention is possible. To make testing
+and experimenting easier, the kernel parameter cgroup_no_v1= allows
+disabling controllers in v1 and make them always available in v2.
+
 
 2-2. Organizing Processes
 

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index cfb2c0f1a4a89237ce131999d7b1cc03aff178b4..0d962a1ff11cd18843cec11c3afd39e9a0a3f68f 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -608,6 +608,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                        cut the overhead, others just disable the usage. So
                        only cgroup_disable=memory is actually worthy}
 
+       cgroup_no_v1=   [KNL] Disable one, multiple, all cgroup controllers in v1
+                       Format: { controller[,controller...] | "all" }
+                       Like cgroup_disable, but only applies to cgroup v1;
+                       the blacklisted controllers remain available in cgroup2.
+
        cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
                        Format: <string>
                        nosocket -- Disable socket memory accounting.