Bug 693883

Summary:	[6.2 FEAT] Turn HARDBARRIER to FLUSH/FUA and perform barrier/flush request consolidation
Product:	Red Hat Enterprise Linux 6	Reporter:	IBM Bug Proxy <bugproxy>
Component:	kernel	Assignee:	Red Hat Kernel Manager <kernel-mgr>
Status:	CLOSED DUPLICATE	QA Contact:	Red Hat Kernel QE team <kernel-qe>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	6.2	CC:	jjarvis, masaharu.nakagawa.dv, msnitzer, nobody+PNT0273897, rwheeler, sbest
Target Milestone:	rc	Keywords:	FutureFeature
Target Release:	---
Hardware:	All
OS:	All
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-04-08 14:17:00 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description IBM Bug Proxy 2011-04-05 19:51:05 UTC

1. Feature Overview:
Feature Id: [71117]
a. Name of Feature: [6.2 FEAT] Turn HARDBARRIER to FLUSH/FUA and perform barrier/flush request
consolidation
b. Feature Description
Reduce Barrier cost by replacing HARDBARRIER with FLUSH/FUA, and also perform barrier consolidations
to reduce unnecessary barrier/flush request.

2. Feature Details:
Sponsor: LTC Filesystems
Architectures:  

Arch Specificity: purely common code
Affects Kernel Modules: Yes
Delivery Mechanism: Backport
Category: kernel
Request Type: Kernel - Enhancement from Upstream
d. Upstream Acceptance: Accepted
Sponsor Priority P2
f. Severity: high
IBM Confidential: No
Code Contribution: IBM code
g. Component Version Target: ---

3. Business Case
Barrier has been enabled as default on local filesystem (ext3/4 and xfs) to add more data
intergirty. The performance penalty with barrier enabled is outstanding. We have seen big drop of
performance on fsync happy workload and database OLTP workload when barrier is turned on (about
50%-75% degradation).  This is critical and unacceptable for DB2. 

4. Primary contact at Red Hat:
John Jarvis, jjarvis

5. Primary contacts at Partner:
Project Management Contact:
Stephanie A. Glass, sglass.com

Technical contact(s):
Mingming Cao, mcao.com

Comment 2 RHEL Program Management 2011-04-05 20:03:53 UTC

Since RHEL 6.1 External Beta has begun, and this bug remains
unresolved, it has been rejected as it is not proposed as
exception or blocker.

Red Hat invites you to ask your support representative to
propose this request, if appropriate and relevant, in the
next release of Red Hat Enterprise Linux.

Comment 3 Mike Snitzer 2011-04-08 14:17:00 UTC

As I recently shared with Mingming Cao (IBM) and Ric Wheeler:

On Tue, Apr 05 2011 at  4:03pm -0400,
Ric Wheeler <rwheeler> wrote:

> I think that this all landed in 6.1 if I understand the BZ correctly.                                                                                                

Not quite all there in 6.1.  The foundation is put in place for 6.1 (it
includes all Tejun's FLUSH/FUA work up to 2.6.38).  AFAIK the request
consolidation piece is referring to "flush merge" (included in 2.6.39).

I ported that flush-merge work to RHEL6 for inclussion in 6.2.  The
patchset is here:
http://people.redhat.com/msnitzer/patches/.rhel6.2/flush_merge/

*** This bug has been marked as a duplicate of bug 672988 ***