In RHEV 3, Host "Memory Page Sharing" status and KSM status does not match

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Virtualization 3.0
  • Red Hat Enterprise Virtualization 3.1

Issue

Sometimes Memory Page Sharing Host information shows Inactive but KSM is running. Or Memory Page Sharing Host information shows Active but KSM is not running.

Resolution

It is already fixed in upstream and must be shipped by the next RHEV versions. Memory Page Sharing will always reflect the current KSM status.

Root Cause

KSM is started or stopped according with ksmtuned policy[1]. On the other hand, the RHEV function checking whether KSM is active or not is called only when a virtual machine is started or stopped. Meanwhile, Administrator Portal can show an outdated information.

A future UI setting for changing this behavior is being tracked in Bugzilla #1026980

[1] - https://access.redhat.com/knowledge/solutions/236253

Diagnostic Steps

Compare the value of Memory Page Sharing in Administration Portal Host General TAB with Host /sys/kernel/mm/ksm/run file value (0 means KSM Inactive and 1 means KSM active).

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