Bug 819965

Summary:	THP page migration
Product:	Red Hat Enterprise Linux 7	Reporter:	Rik van Riel <riel>
Component:	kernel	Assignee:	Aristeu Rozanski <arozansk>
kernel sub component:	Memory Management	QA Contact:	Li Wang <liwan>
Status:	CLOSED DEFERRED	Docs Contact:
Severity:	unspecified
Priority:	unspecified	CC:	aarcange, aquini, cye, jshortt, juzhang, knoel, knweiss, liwan, lwoodman, mm-maint, tburke, vcojot
Version:	7.0	Keywords:	FutureFeature, Reopened
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-07-20 20:44:35 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:
Bug Depends On:
Bug Blocks:	817917, 919431, 1032535, 1032538, 1071730, 1296180, 1394638, 1469551

Description Rik van Riel 2012-05-08 18:28:49 UTC

Description of problem:

Currently, page migration breaks 2MB pages into 4kB pages, which then have to be reassembled again at the destination. This negates a lot of the performance benefits of doing NUMA relocations in the first place.

2MB transparent hugepages should stay intact across page migration.

We can use the same bit that is used to protect 2MB->4kB and 4kB->2MB transitions to block out page accesses during a 2MB->2MB transition.

Comment 5 Johannes Weiner 2013-09-03 21:16:09 UTC

THP-preserving migration is included in the NUMA balancing code.

Comment 6 Rik van Riel 2013-11-20 13:45:13 UTC

Johannes,

if you look unmap_and_move, which is indirectly called from sys_migrate_pages, you will see that it does NOT preserve THP on migration. There is a reason this bug was opened separately.

Comment 7 Johannes Weiner 2013-11-21 17:03:02 UTC

(In reply to Rik van Riel from comment #6)
> Johannes,
> 
> if you look unmap_and_move, which is indirectly called from
> sys_migrate_pages, you will see that it does NOT preserve THP on migration.
> There is a reason this bug was opened separately.

My bad, I was under the assumption this was to track the side-project of adding THP-preserving migration to AutoNUMA.

I'll dig up the patches.

Comment 8 Ludek Smid 2014-06-26 10:42:53 UTC

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.

Comment 9 Ludek Smid 2014-06-26 11:16:36 UTC

The comment above is incorrect. The correct version is bellow.
I'm sorry for any inconvenience.
---------------------------------------------------------------

This request was NOT resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you need
to escalate this bug.