Bug 1717007

Created attachment 1577147 [details]
engine and screenshots

Description of problem:"Max free Memory for scheduling new VMs:" is not released after VM is migrated from the host. The initial memory on the host is 30454 MB , HE VM is migrated to this host , the  "Max free Memory for scheduling new VMs: is decreased to the 13838 MB , though afterward when the VM is migrated from this host the memory remains 13838 MB. So, in this way after several migrations (balancing) the host has "Max free Memory for scheduling new VMs:" = 0 while no VM is running on this host. and as a result, no VM could be started there.

vdsm-client see it correctly, also Physical Memory: in engine is shown correctly . the problem is with "Max free Memory for scheduling new VMs: which could in this way be 0 and prevent from running VMs on this host while actually, no VM resides there. After the host reboot, the problem remains. it is released if I remove the host from the engine and -re-install


Version-Release number of selected component (if applicable):ovirt-engine-4.3.4.2-0.1.el7.noarch


How reproducible: reproduced while tier3 automation run , and afterward manualy after several times migration/balancing of HE VM (it could be also regular VM, just configured with 16384 MB, so faster and easier to see the memory decreasing ).


Steps to Reproduce:
There is no well-defined scenario - it happened after a lot of migration/balancing of HE VM. 

Actual results: Max free Memory for scheduling new VMs: 0 MB while actually, no VMs run on host 

Expected results: memory must be freed.

Additional info: from discussion with Andrej:

I have looked at the environment, and it looks like the cause is the same as for the issue we have discussed yesterday.
Balancing a VM does not release the reserved memory, when the VM is scheduled to the same host.

Querying the DB on the engine machine we see:

engine=# select vds_name, pending_vcpus_count, pending_vmem_size from vds;
   vds_name   | pending_vcpus_count | pending_vmem_size 
--------------+---------------------+-------------------
 host_mixed_2 |                   0 |                 0
 host_mixed_1 |                   5 |             17786
 host_mixed_3 |                   0 |                 0
(3 rows)

The reserved resources on host_mixed_1 are not released.

The patch that should fix it in 4.3 was merged today: https://gerrit.ovirt.org/#/c/100530/

As a workaround, the pending resources are released when the ovirt-engine service is restarted.