Bug 1114205

Summary: memory overcommitment & vm online migration -> can lead to heavy swap
Product: [Retired] oVirt Reporter: Markus Stockhausen <mst>
Component: ovirt-engine-coreAssignee: bugs <bugs>
Status: CLOSED DUPLICATE QA Contact: Pavel Stehlik <pstehlik>
Severity: high Docs Contact:
Priority: unspecified    
Version: 3.4CC: acathrow, dfediuck, gklein, iheim, yeylon
Target Milestone: ---   
Target Release: 3.6.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: sla
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2014-09-03 15:18:56 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: SLA RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Markus Stockhausen 2014-06-28 16:21:46 UTC 
Description of problem:

heavy paging if VM is migrated to target host with less memory available than VM is using

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

ovirt 3.4.2 

How reproducible:

100%

Steps to Reproduce:

- cluster defined with 150% memory overcommitment + ksm enabled
- administrator wants to move a VM to a selected target host
- VM has X GB memory
- Target host has less than X GB free memory
- Due to overcommitment engine allows to move VM to target host

Actual results:

- OVirt starts migrationg VM
- Target host runs out of memory
- paging starts
- Host & VMs stall

Expected results:

- Either a warning should be displayed or migration should be disabled.

Additional info:

Indepedent from the configured overcommitment/ksm policy OVirt should compare memory of VM to migrate versus free memory on target host. KSM might compress memory afterwards but this is too late for the migration process itself.
Comment 1 Doron Fediuck 2014-09-03 15:18:56 UTC 
Markus, 
thanks for the detailed report. This is a result of current considerations
while doing balancing and migration, and it will be fixed as a part
of Bug 1093038.

*** This bug has been marked as a duplicate of bug 1093038 ***