Note: This bug is displayed in read-only format because the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

Bug 1025138

Summary: Read/Randread/Randrw performance regression
Product: Red Hat Enterprise Linux 7 Reporter: Xiaomei Gao <xigao>
Component: qemu-kvmAssignee: Fam Zheng <famz>
Status: CLOSED CURRENTRELEASE QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: high    
Version: 7.0CC: acathrow, areis, bsarathy, hhuang, juzhang, kwolf, michen, mkenneth, qzhang, stefanha, virt-maint, wquan, xigao
Target Milestone: rcKeywords: Regression
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: qemu-kvm-1.5.3-20.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: 1022548 Environment:
Last Closed: 2014-06-13 13:07:02 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: 1022548    
Bug Blocks: 1028252    

Comment 1 Xiaomei Gao 2013-10-31 06:07:03 UTC 
The issue can be reproduced on RHEL7 version. Downgrade my qemu-kvm version and found the regression was introduced on qemu-kvm-1.5.3-7.el7 which has the following patch:
- kvm-block-Produce-zeros-when-protocols-reading-beyond-en.patch [bz#1007226]

Test Steps:
1.Create a data disk on Netapp NFS server
   # mount -t nfs -o rw,bg,hard,nointr,rsize=65536,wsize=65536,tcp,noac,vers=3,timeo=600  192.168.0.113:/vol/s2wquan116171nfs /home/kvm_autotest_root/images
   # qemu-img create -f raw /home/kvm_autotest_root/images/storage2.raw 40G

2.Boot guest with data disk
  /usr/libexec/qemu-kvm  \
    -name 'virt-tests-vm1' \
    -nodefaults \
    -drive file='/home/kvm_autotest_root/images/RHEL-Server-6.5-64.raw',index=0,if=none,id=drive-virtio-disk1,media=disk,cache=none,snapshot=off,format=raw,aio=threads \
    -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk1,bootindex=0 \
    -drive file='/home/kvm_autotest_root/images/storage2.raw',index=2,if=none,id=drive-virtio-disk2,media=disk,cache=none,snapshot=off,format=raw,aio=threads \
    -device virtio-blk-pci,bus=pci.0,addr=0x5,drive=drive-virtio-disk2,bootindex=1 \
    -device virtio-net-pci,netdev=idqUIcQC,mac='9a:37:37:37:37:9e',bus=pci.0,addr=0x6,id='idT1SAVS' \
    -netdev tap,id=idqUIcQC,vhost=on \
    -m 4096 \
    -smp 2,maxcpus=2,cores=1,threads=1,sockets=2 \
    -cpu 'Westmere' \
    -M rhel6.5.0 \
    -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1 \
    -vnc :0 \
    -vga cirrus \
    -rtc base=utc,clock=host,driftfix=slew  \
    -boot order=cdn,once=c,menu=off   \
    -no-kvm-pit-reinjection \
    -device sga \
    -enable-kvm

3. In guest
   # i=`/bin/ls /dev/[vs]db` &&  mkfs.ext4 $i -F > /dev/null; partprobe; umount /mnt; mount $i /mnt && echo 3 > /proc/sys/vm/drop_caches && sleep 3
   # fio --rw=read --bs=4k --iodepth=1 --runtime=1m --direct=1 --filename=/mnt/read_4k_1 --name=job1 --ioengine=libaio --thread --group_reporting --numjobs=16 --size=512MB --time_based --ioscheduler=deadline 

4. Test Results:
qemu-kvm-1.5.3-10.el7 --- bad
bw=24247KB/s, iops=6061

qemu-kvm-1.5.3-6.el7  --- good
bw=60174KB/s, iops=15043

qemu-kvm-1.5.3-7.el7  --- bad
bw=20697KB/s, iops=5174
Comment 4 Miroslav Rezanina 2013-11-28 07:35:32 UTC 
Fix included in qemu-kvm-1.5.3-20.el7
Comment 8 Ludek Smid 2014-06-13 13:07:02 UTC 
This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.