Bug 1976679

Summary:	blk-mq: fix/improve io scheduler batching dispatch
Product:	Red Hat Enterprise Linux 8	Reporter:	Ming Lei <minlei>
Component:	kernel	Assignee:	Ming Lei <minlei>
kernel sub component:	Block Layer	QA Contact:	ChanghuiZhong <czhong>
Status:	CLOSED ERRATA	Docs Contact:
Severity:	unspecified
Priority:	unspecified	CC:	acaringi, jmoyer
Version:	8.5
Target Milestone:	beta
Target Release:	8.5
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	kernel-4.18.0-327.el8	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-11-09 19:18:09 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 Ming Lei 2021-06-28 02:24:08 UTC

Description of problem:

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-5.14/block&id=613471549f366cdf4170b81ce0f99f3867ec4d16

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit/?h=for-5.14/block&id=cb9516be7708a2a18ec0a19fe3a225b5b3bc92c7

One patch is for avoiding to dequeue two many requests, so io merge can be
improved.

Another patch is for fixing batching dispatch, in which hctx->dispatch_busy
is evaluated, but not get updated.

Comment 6 ChanghuiZhong 2021-08-04 08:58:03 UTC

sanity test passed with kernel-4.18.0-327.el8:
https://beaker.engineering.redhat.com/jobs/5654211
https://beaker.engineering.redhat.com/jobs/5655252

All fix patches has included to kernel tree:
$ git log kernel-4.18.0-327.el8 --oneline --grep=1976679
14b1478fd252 Merge: block: improve batching dispatch and fix discard request merge
377ced4accb4 blk-mq: update hctx->dispatch_busy in case of real scheduler
40aa7107656c block: Do not pull requests from the scheduler when we cannot dispatch them

move to verified + sanityonly

Comment 9 errata-xmlrpc 2021-11-09 19:18:09 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: kernel security, bug fix, and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2021:4356