Bug 916418

Summary: virtio_scsi block performance degradation when block size is 4/8/16 and iodepth is 64
Product: Red Hat Enterprise Linux 6 Reporter: Xiaomei Gao <xigao>
Component: qemu-kvmAssignee: Fam Zheng <famz>
Status: CLOSED DUPLICATE QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: medium    
Version: 6.4CC: acathrow, bsarathy, juzhang, michen, mkenneth, qzhang, virt-maint, wquan, xigao
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-08-18 00:37:56 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:

Comment 2 RHEL Program Management 2013-03-04 06:47:20 UTC 
This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.
Comment 7 Fam Zheng 2014-08-15 07:41:21 UTC 
The enabling of ioeventfd on 6.6 and 6.5.z makes a huge difference. Testing the sequential read can tell this:

RHEL 6.4
==============================================================
bs         iodepth    jobs       bw         iops       latency
--------------------------------------------------------------
4k         64         1          151        38872      1626


RHEL 6.5
==============================================================
bs         iodepth    jobs       bw         iops       latency
--------------------------------------------------------------
4k         64         1          517        132413     478


RHEL 6.6
==============================================================
bs         iodepth    jobs       bw         iops       latency
--------------------------------------------------------------
4k         64         1          491        125940     503


RHEL 6.6 - but disable ioeventfd
==============================================================
bs         iodepth    jobs       bw         iops       latency
--------------------------------------------------------------
4k         64         1          123        31641      2005


So I think this BZ can be closed. Xiaomei, could you confirm?
Comment 9 Fam Zheng 2014-08-18 00:37:56 UTC 

*** This bug has been marked as a duplicate of bug 1123271 ***
Comment 10 Qunfang Zhang 2014-08-18 01:07:27 UTC 

*** This bug has been marked as a duplicate of bug 1106420 ***