Consider for compact memory before running VM

Description Somtimes my VMs can’t start with the next error:

[Z0][VMM][I]: error: internal error: process exited while connecting to monitor: ioctl(KVM_CREATE_VM) failed: 12 Cannot allocate memory
[Z0][VMM][I]: failed to initialize KVM: Cannot allocate memory

But after echo 1 > /proc/sys/vm/compact_memory everything start working fine.

My idea is to add this action to the kvm driver, and call it before any VM is start.

Use case

Avoid problems caused with high memory fragmentation on the host.

More info here: https://stackoverflow.com/questions/46464785/cannot-allocate-memory-despite-free-reporting-available

Interface Changes

Modify deploy action for the kvm driver.

Progress Status

• Branch created
• Code committed to development branch
• Testing - QA
• Documentation
• Release notes - resolved issues, compatibility, known issues
• Code committed to upstream release/hotfix branches
• Documentation committed to upstream release/hotfix branches

[kvaps]

Yes, we’re using the patch form https://github.com/OpenNebula/one/pull/3126, and set COMPACT_MEMORY=yes already for one year, we are started having less problem connected with this error, but sometimes they are still happening.

Today I’ve tried echo 3 > /proc/sys/vm/drop_caches as well and my VM is started working fine after that

[vholer]

Implemented as configurable feature by @paczerny http://docs.opennebula.io/5.13/installation_and_configuration/open_cloud_host_setup/kvm_driver.html#compact-memory-optional