Re: [PATCH] doc: cgroup: correct the wrong information about measure of memory pressure

From: Yang Shi
Date: Thu Feb 21 2019 - 14:54:58 EST

On 2/19/19 2:45 AM, çèé wrote:
Hi TeJun
I've built the 5.0.0-rc6 kernel with psi option, but I cannot find any
cgroup.controllers when I mounted cgroup2.

[root@bogon /]# uname -r
[root@bogon /]# 5.0.0-rc6+
[root@bogon /]# mount -t cgroup2 none cgroup2/
[root@bogon /]# cat cgroup2/cgroup.controllers
[root@bogon /]
[root@bogon /]# cat cgroup2/cgroup.subtree_control
[root@bogon /]#

What's wrong with this kernel? Or maybe I lost some mount option?

I'm not sure what you did before you mounted cgroup2, but if you have legacy controllers mounted, you have to unmount them, otherwise cgroup.controllers would show up as empty. Or you can pass "cgroup_no_v1=" in your kernel parameter.



Tejun Heo <tj@xxxxxxxxxx> ä2019å2æ19æåä äå10:32åéï
On Sat, Feb 16, 2019 at 08:56:04AM +0800, Yang Shi wrote:
Since PSI has implemented some kind of measure of memory pressure, the
statement about lack of such measure is not true anymore.

Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Documentation/admin-guide/cgroup-v2.rst | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 7bf3f12..9a92013 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -1310,8 +1310,7 @@ network to a file can use all available memory but can also operate as
performant with a small amount of memory. A measure of memory
pressure - how much the workload is being impacted due to lack of
memory - is necessary to determine whether a workload needs more
-memory; unfortunately, memory pressure monitoring mechanism isn't
-implemented yet.
Maybe refer to PSI?