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Bug 783950 - RFE: Backport corountine-based block layer
Summary: RFE: Backport corountine-based block layer
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm
Version: 6.3
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Kevin Wolf
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 582475 748534 748906 782029 802284 806432 812085 813953
TreeView+ depends on / blocked
 
Reported: 2012-01-23 10:42 UTC by Kevin Wolf
Modified: 2015-02-28 03:14 UTC (History)
12 users (show)

Fixed In Version: qemu-kvm-0.12.1.2-2.228.el6
Doc Type: Enhancement
Doc Text:
Improved access to qcow2 disk images KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.
Clone Of:
Environment:
Last Closed: 2012-06-20 11:38:44 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2012:0746 0 normal SHIPPED_LIVE qemu-kvm bug fix and enhancement update 2012-06-19 19:31:48 UTC

Description Kevin Wolf 2012-01-23 10:42:28 UTC 
Features like live block copy/image streaming make heavy use of the coroutine-based block layer infrastructure in upstream qemu. We need to backport the whole infrastructure before we can make use of it in new features.

As a side effect, this fixes the bug that image formats like qcow2 block the VCPU during I/O requests. The problem can be reproduced with jitterd, which reports problems on the current RHEL package, but doesn't any more when the coroutine patches are applied:

    * http://git.codemonkey.ws/cgit/jitterd.git/
    * Options used in earlier testing: ./jitterd -f -m 2 -p 100 -r 10
Comment 3 Ademar Reis 2012-04-16 23:57:03 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
qemu-kvm in RHEL6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.
Comment 4 Martin Prpič 2012-04-17 12:00:05 UTC 
    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -1 +1,3 @@
-qemu-kvm in RHEL6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.+Improved access to qcow2 disk images
+
+KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.
Comment 5 Dor Laor 2012-04-22 11:30:42 UTC 
    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -1,3 +1 @@
-Improved access to qcow2 disk images
+No documentation needed-
-KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.
Comment 6 Ademar Reis 2012-04-23 23:58:51 UTC 
    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -1 +1,5 @@
-No documentation needed+Improved access to qcow2 disk images
+
+KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images
+(qcow2 is the default format) by making it more asynchronous, thus avoiding
+vCPU stalls and enhancing the overall performance during disk I/O.
Comment 7 Ademar Reis 2012-04-23 23:59:10 UTC 
    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -1,5 +1,3 @@
 Improved access to qcow2 disk images
 
-KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images
+KVM in Red Hat Enterprise Linux 6.3 improved the access to qcow2 disk images (qcow2 is the default format) by making it more asynchronous, thus avoiding vCPU stalls and enhancing the overall performance during disk I/O.-(qcow2 is the default format) by making it more asynchronous, thus avoiding
-vCPU stalls and enhancing the overall performance during disk I/O.
Comment 8 Quan Wenli 2012-05-02 09:56:24 UTC 
Hi,kwolf

Since qemu-kvm-278 is the mirroring implementation first merged and qemu-kvm-261 is the image streaming implementation first merged,i could not reproduce this bug through live block copy/image streaming w/ the qemu version prior to -228,Do you have any suggestion to reproduce it?
Or is it possible reproduce it w/ qemu which is removed the patchset of backport corountine-based block layer from latest qemu-kvm, if it can, could you build one for me reproduce it?

Thanks 
wenli
Comment 9 Paolo Bonzini 2012-05-02 13:06:14 UTC 
Coroutine-based block layer is required for streaming and mirroring, so it's not possible to test them without coroutines.

This bug is really about a rewrite of some parts of the block layer; even though it does have some visible effects listed in the release notes, it is mostly an enabler for streaming and mirroring.  Since qcow2 is already tested by the regular test plan, SanityOnly verification should be enough.
Comment 10 Quan Wenli 2012-05-04 06:04:07 UTC 
(In reply to comment #9)
> Coroutine-based block layer is required for streaming and mirroring, so it's
> not possible to test them without coroutines.
> 
> This bug is really about a rewrite of some parts of the block layer; even
> though it does have some visible effects listed in the release notes, it is
> mostly an enabler for streaming and mirroring.  Since qcow2 is already tested
> by the regular test plan, SanityOnly verification should be enough.

Thanks Paolo.

I verified it w/ qemu-kvm-rhev-290,through monitor jitter by "./jitterd -f -m 2 -p 100 -r 10" on the guest while streaming,there is no chatter greater than 200 millisecond(s).So,I change it to verified.
Comment 11 errata-xmlrpc 2012-06-20 11:38:44 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.

http://rhn.redhat.com/errata/RHBA-2012-0746.html
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