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Bug 602417 - Enable VIRTIO_RING_F_PUBLISHED bit for all virtio devices
Summary: Enable VIRTIO_RING_F_PUBLISHED bit for all virtio devices
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm
Version: 6.0
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: Amit Shah
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2010-06-09 19:52 UTC by Jes Sorensen
Modified: 2013-01-09 22:43 UTC (History)
9 users (show)

Fixed In Version: qemu-kvm-0.12.1.2-2.81.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2010-11-10 21:25:33 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
Patch to enable vring idx publish bit (955 bytes, patch)
2010-06-09 19:52 UTC, Jes Sorensen 		no flags Details | Diff
View All

Description Jes Sorensen 2010-06-09 19:52:19 UTC 
Created attachment 422676 [details]
Patch to enable vring idx publish bit

Description of problem:
We support vring idx publishing for vhost_net, enable it for virtio_blk as well.

Version-Release number of selected component (if applicable):


How reproducible:

Steps to Reproduce:
1.
2.
3.
  
Actual results:


Expected results:


Additional info:
This is a patch to enable the vring idx publishing for virtio_blk, which can reduce the VMEXIT count by upto 20% on some benchmarks, such as IOZone.

The vring idx publishing is already enabled for vhost_net, this patch enables it for virtio_blk as well.
Comment 2 RHEL Program Management 2010-06-09 20:12:56 UTC 
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.
Comment 4 Amit Shah 2010-06-17 14:50:12 UTC 
Updating the summary to note that we should do this for all the virtio devices, namely net, block and serial, and instead of handling each one separately, we can enable them all at once. I'll post a new patch for this shortly.
Comment 8 Dor Laor 2010-07-07 09:32:20 UTC 
Why need info flag is set?
Comment 9 Haruo Tomita 2010-07-07 22:31:16 UTC 
(In reply to comment #8)
> Why need info flag is set?

I'm sorry. I typo.
Comment 10 Mike Cao 2010-07-08 09:16:45 UTC 
Compared Guest's I/O and net performance between qemu-kvm-0.12.1.2-2.91.el6 and qemu-kvm-0.12.1.2-2.77.el6

Steps:
1.Start VM by using :
/usr/libexec/qemu-kvm -cpu qemu64,+sse2,+x2apic -smp 1 -m 2G -rtc-td-hack -balloon virtio -drive file=RHEL-Server-5.5-64-virtio.raw,media=disk,cache=none,format=raw,if=none,werror=stop,rerror=stop,id=drive-virtio0-0 -device virtio-blk-pci,drive=drive-virtio0-0,id=drive-virtio0-0 -device virtio-net-pci,netdev=hostnet0,mac=00:23:55:2a:12:66 -netdev tap,id=hostnet0,vhost=on -uuid `uuidgen` -boot order=c -vnc :2 -monitor stdio -qmp tcp:0:4444,server,nowait

2.testing I/O performance by using #iozone -az -n 4g -g 4g -r 64k -i 0 -i 1 

3 testing net performance by using #netperf -H <ip> -l 60

Actual Results:

after step2,
                  qemu-kvm-0.12.1.2-2.77	qemu-kvm-0.12.1.2-2.91 
Writer Report		89342				89474
Re-writer Report	86229				89779
Reader Report		85046				88085
Re-reader Report	89048				89257

after step3,
                 	 qemu-kvm-0.12.1.2-2.77		qemu-kvm-0.12.1.2-2.91 
throughput10^6b/s		13958.81			21764.45
throughput10^6b/s		13084.79			13747.95

Above all ,after enable VIRTIO_RING_F_PUBLISHED bit,the net and block I/O can use successfully, and the performance of block I/O and net were not getting worse.

This issue can be closed.
Comment 11 releng-rhel@redhat.com 2010-11-10 21:25:33 UTC 
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.
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