Bug 1394033

Summary:	mkfs.gfs2: Increase default resource group size
Product:	Red Hat Enterprise Linux 8	Reporter:	Andrew Price <anprice>
Component:	gfs2-utils	Assignee:	Andrew Price <anprice>
Status:	CLOSED WONTFIX	QA Contact:	cluster-qe <cluster-qe>
Severity:	unspecified	Docs Contact:
Priority:	medium
Version:	8.0	CC:	cluster-maint, gfs2-maint, rhandlin, sbradley, swhiteho
Target Milestone:	rc	Keywords:	Triaged
Target Release:	8.2
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2020-12-01 07:27:35 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:
Bug Depends On:
Bug Blocks:	1111393, 1497636

Description Andrew Price 2016-11-10 21:03:52 UTC

For RHEL 7 the default (target) resource group size was set to 2G but then a performance problem was discovered (bug #1154782) which caused the default size to be reverted to 256M in RHEL 7.1 (bug #1162817).

We should reassess whether those performance issues have been solved and increase the default resource group size back to 2G when they are. fsck.gfs2 performance is also a factor here but, theoretically, fewer resource groups should allow fsck.gfs2 to go faster.

Comment 1 Nate Straz 2017-04-07 15:09:31 UTC

There may be an issue with performance at larger RG sizes with multiple processes.  I ran a matrix of RG size vs processes and got these results:

RG size  procs   bandwidth   
  256      1    539466KB/s
  512      1    537059KB/s
 1024      1    560422KB/s
 2048      1    552481KB/s

  256      3    472423KB/s
  512      3    368493KB/s
 1024      3    354238KB/s
 2048      3    343896KB/s

  256      6    508019KB/s
  512      6    422882KB/s
 1024      6    313730KB/s
 2048      6    275803KB/s

  256     12    546520KB/s
  512     12    390912KB/s
 1024     12    284684KB/s
 2048     12    198894KB/s

Comment 2 Steve Whitehouse 2017-04-07 15:12:31 UTC

Is that because they are all using the same rgrp? If each thread runs in a different top level dir (or subdir of a different top level dir) then does that issue go away?

Comment 3 Nate Straz 2017-04-07 18:03:24 UTC

You have a point.  I figured out how to accomplish that with fio and here are the results:

RG size  procs   bandwidth   
  256      1    537019KB/s
  512      1    547736KB/s
 1024      1    565922KB/s
 2048      1    530186KB/s

  256      3    606669KB/s
  512      3    563094KB/s
 1024      3    718381KB/s
 2048      3    559343KB/s

  256      6    665150KB/s
  512      6    577753KB/s
 1024      6    676871KB/s
 2048      6    573286KB/s

  256     12    666406KB/s
  512     12    670210KB/s
 1024     12    654321KB/s
 2048     12    696050KB/s

Comment 11 RHEL Program Management 2020-12-01 07:27:35 UTC

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.