Bug 1628191

Summary: ~40% virtio_blk disk performance drop for win2012r2 guest when comparing qemu-kvm-rhev-2.12.0-9 with qemu-kvm-rhev-2.12.0-12
Product: Red Hat Enterprise Linux 7 Reporter: Yanhui Ma <yama>
Component: qemu-kvm-rhevAssignee: Fam Zheng <famz>
Status: CLOSED ERRATA QA Contact: Yanhui Ma <yama>
Severity: high Docs Contact:
Priority: urgent    
Version: 7.6CC: areis, chayang, famz, juzhang, kwolf, michen, mtessun, pbonzini, virt-maint, wquan, yama
Target Milestone: rcKeywords: Regression
Target Release: ---   
Hardware: x86_64   
OS: Unspecified   
Whiteboard:
Fixed In Version: qemu-kvm-rhev-2.12.0-17.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
: 1632622 (view as bug list) Environment:
Last Closed: 2018-11-01 11:13:32 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: 1632622    

Comment 4 Paolo Bonzini 2018-09-12 15:48:19 UTC 
I think the culprit is "Don't count ctx->notifier as progress when polling".  It causes aio_poll to do the poll system call before invoking aio_bh_poll().  I followed up in the qemu-devel mailing list.
Comment 10 Miroslav Rezanina 2018-09-19 16:54:40 UTC 
Fix included in qemu-kvm-rhev-2.12.0-17.el7
Comment 19 errata-xmlrpc 2018-11-01 11:13:32 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, 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/RHBA-2018:3443