Bug 1289291 - Live Migration dynamic cpu throttling for auto-convergence (RHEL OSP)
Live Migration dynamic cpu throttling for auto-convergence (RHEL OSP)
Product: Red Hat OpenStack
Classification: Red Hat
Component: openstack-nova (Show other bugs)
8.0 (Liberty)
Unspecified Unspecified
medium Severity medium
: ga
: 10.0 (Newton)
Assigned To: Eoghan Glynn
: FutureFeature
Depends On: 1289285
Blocks: 1289288 1289290 1358141
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Reported: 2015-12-07 15:20 EST by Hai Huang
Modified: 2016-07-20 03:29 EDT (History)
14 users (show)

See Also:
Fixed In Version:
Doc Type: Enhancement
Doc Text:
Story Points: ---
Clone Of: 1289285
Last Closed: 2016-02-19 10:57:12 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Hai Huang 2015-12-07 15:20:35 EST
+++ This bug was initially created as a clone of Bug #1289285 +++

Description of problem:

With extreme memory write intensive workloads, normal live migration will never complete because the guest is writing to memory faster than Qemu can transfer the memory changes to the destination system. In this case normal migration will continue forever, not making enough progress to stop the guest and proceed to the non-live "finishing up" phase of migration.

This feature provides a method for slowing down guest execution speed, thus hopefully, also slowing down guest memory write speed. As time advances autoconverge will continually increase the amount of guest cpu throttling until guest memory write speed slows enough to allow the guest to be stopped and migration to finish.

As of Qemu 2.5 dynamic throttling has been added to autoconverge dramatically increasing its effectiveness.

This feature will be available in RHEL7.3 qemu-kvm-rhev with the rebase 
to qemu 2.5.

The qemu feature page can be found in:

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


How reproducible:

Steps to Reproduce:
Please refer to the qemu feature page above.

Actual results:
Live migration fails due to high page dirty rate 
(i.e. intensive memory writes).

Expected results:
Live migration successfully complete.

Additional info:
Comment 2 Perry Myers 2015-12-15 17:13:52 EST
This is clearly a Nova feature, moving it from RFEs back to Nova. Please leave it there.

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