Bug 1278985

Summary:	Fedora should be compiled with CONFIG_CMA=y to enable Contiguous Memory Allocator
Product:	[Fedora] Fedora	Reporter:	hkimura <hideaki.kimura>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	low	Docs Contact:
Priority:	unspecified
Version:	23	CC:	gansalmon, itamar, jonathan, kernel-maint, labbott, madhu.chinakonda, mchehab, pbrobinson
Target Milestone:	---
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-03-22 22:00:12 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 hkimura 2015-11-06 23:05:41 UTC

Description of problem:
Both Fedora 23 Workstation and Server do not enable CMA (Contiguous Memory Allocator), which is required for a few new features, such as 1GB hugepage allocation/deallocation at _runtime_: https://lwn.net/Articles/594435/

RHEL 7.1 and later already enabled this, so why not.
This will benefit various big-memory applications and DMA applications that use CMA.

To enable CMA, please add "CONFIG_CMA=y" to .config for kernel compilation.

Version-Release number of selected component (if applicable):
FC23 (Kernel 4.2.5 as of today)

How reproducible:
Always

Steps to Reproduce:
1. (to check the current config) grep CONFIG_CMA /boot/config*
2.
3.

Actual results:
Just says: "# CONFIG_CMA is not set"

Expected results:
Has the line: "CONFIG_CMA=y"



Additional info:
Ubuntu enabled it long ago (at least in UB1404) probably for DMA applications. RHEL did it too since 7.1 and onwards.

Comment 1 Laura Abbott 2015-11-10 17:40:19 UTC

I'll turn this on in rawhide for x86_64. CMA is mostly stable now but it's a big enough change that turning it on in stable releases really calls for more testing.

Comment 2 hkimura 2015-11-11 22:01:12 UTC

Thanks, I'll try rawhide when you push the change.

Comment 3 Peter Robinson 2015-11-12 11:25:40 UTC

(In reply to Laura Abbott from comment #1)
> I'll turn this on in rawhide for x86_64. CMA is mostly stable now but it's a
> big enough change that turning it on in stable releases really calls for
> more testing.

Just as a data point we've had it enabled in ARMv7 for some time as it was needed there for some display support.

Comment 4 Peter Robinson 2016-03-22 22:00:12 UTC

In at least Fedora 23 in 4.4+