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Bug 1953515

Summary:	Make cgroupv2 as default in RHEL9.0
Product:	Red Hat Enterprise Linux 9	Reporter:	Chao Ye <cye>
Component:	kernel	Assignee:	Waiman Long <llong>
kernel sub component:	Control Groups	QA Contact:	Chao Ye <cye>
Status:	CLOSED CURRENTRELEASE	Docs Contact:	Jaroslav Klech <jklech>
Severity:	unspecified
Priority:	unspecified	CC:	arozansk, jklech, llong, longman
Version:	9.0	Keywords:	TestOnly, Triaged
Target Milestone:	beta	Flags:	pm-rhel: mirror+
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:	.`cgroup-v2` enabled by default in RHEL 9 The control groups version 2 (`cgroup-v2`) feature implements a single hierarchy model that simplifies the management of control groups. Also, it ensures that a process can only be a member of a single control group at a time. Deep integration with `systemd` improves the end-user experience when configuring resource control on a RHEL system. Development of new features is mostly done for `cgroup-v2`, which has some features that are missing in `cgroup-v1`. Similarly, `cgroup-v1` contains some legacy features that are missing in `cgroup-v2`. Also, the control interfaces are different. Therefore, third party software with direct dependency on `cgroup-v1` may not run properly in the `cgroup-v2` environment. To use `cgroup-v1`, you need to add the following parameters to the kernel command-line: ---- systemd.unified_cgroup_hierarchy=0 systemd.legacy_systemd_cgroup_controller ---- NOTE: Both `cgroup-v1` and `cgroup-v2` are fully enabled in the kernel. There is no default control group version from the kernel point of view, and is decided by `systemd` to mount at startup.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-10-19 01:28:28 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Chao Ye 2021-04-26 09:43:02 UTC

Description of problem:
Tracking bug for cgroupv2 default enablement in RHEL9.0

Version-Release number of selected component (if applicable):


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Comment 1 Waiman Long 2021-04-26 14:46:03 UTC

(In reply to Chao Ye from comment #0)
> Description of problem:
> Tracking bug for cgroupv2 default enablement in RHEL9.0

Please note that both cgroup v1 and v2 are fully enabled in the kernel. There is no default from the kernel point of view. The cgroup default is what systemd decides to mount. If it mounts cgroup v2 at startup, v2 is the default. If it mounts cgroup v1 instead, v1 will be the default.

-Longman