Bug 1537045

+++ This bug was initially created as a clone of Bug #1519054 +++

Description of problem:
Bug in log output in hardware.py "Not enough available memory to schedule instance" prints full memory instead of available memory

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


Additional info:

When nova fails scheduling, it will print:
~~~
2017-11-29 10:50:16.904 325123 DEBUG nova.virt.hardware [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] Not enough available memory to schedule instance. Oversubscription is not possible with pinned instances. Required: 32768, actual: 65406 _numa_fit_instance_cell_with_pinning /usr/lib/python2.7/site-packages/nova/virt/hardware.py:845
2017-11-29 10:50:16.904 325123 DEBUG oslo_concurrency.lockutils [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] Lock "compute_resources" released by "nova.compute.resource_tracker.instance_claim" :: held 0.021s inner /usr/lib/python2.7/site-packages/oslo_concurrency/lockutils.py:282
2017-11-29 10:50:16.905 325123 DEBUG nova.compute.manager [req-b62c53d2-13db-4fac-a125-409b4f046418 8f883df20fce46dbef3ce634610c51be53b87e658359f05b7eba1062ce7e5d8b 5b54e36678a542d899f1ff62268fc25a - - -] [instance: 86cc16bd-5f51-402b-aa03-01ab0c3ffaf4] Insufficient compute resources: Requested instance NUMA topology cannot fit the given host NUMA topology. _build_and_run_instance /usr/lib/python2.7/site-packages/nova/compute/manager.py:1934
~~~

This of course looks very confusing (we need 32 GB, we have 64, so why is this failing?).

The problem here is the log output, which is flawed --- /usr/lib/python2.7/site-packages/nova/virt/hardware.py:
~~~
    840     if host_cell.avail_memory < instance_cell.memory:
    841         LOG.debug('Not enough available memory to schedule instance. '
    842                   'Oversubscription is not possible with pinned instances. '
    843                   'Required: %(required)s, actual: %(actual)s',
    844                   {'required': instance_cell.memory,
    845                    'actual': host_cell.memory})
    846         return
~~~

This should be:
~~~
    840     if host_cell.avail_memory < instance_cell.memory:
    841         LOG.debug('Not enough available memory to schedule instance. '
    842                   'Oversubscription is not possible with pinned instances. '
    843                   'Required: %(required)s, actual: %(actual)s',
    844                   {'required': instance_cell.memory,
    845                    'actual': host_cell.avail_memory})
    846         return
~~~

Or even better:
~~~
    840     if host_cell.avail_memory < instance_cell.memory:
    841         LOG.debug('Not enough available memory to schedule instance. '
    842                   'Oversubscription is not possible with pinned instances. '
    843                   'Required: %(required)s, actual: %(actual)s, total: %(total)s',
    844                   {'required': instance_cell.memory,
    845                    'actual': host_cell.avail_memory,
    846                    'total': host_cell.memory})
    847         return
~~~

--- Additional comment from Sahid Ferdjaoui on 2017-11-30 03:44:05 EST ---

Thanks for the fix upstream. While merged I will take care of doing the backport.