Clarify min memory requirement (512MB) of dpm partition

[Andreas Scheuring]

A DPM partition must requires at least 512MB memory:

initial-memory property:
"The initial amount of memory to assign to the partition
when it is started, specified in MB. This value must be at
least 512, and it must be less than or equal to the value of
maximum-memory.
Default: 1024" [1]

We need to clarify how this affects us
- Should max_memory also have a minimum value of 512?
- Is rounding happening (up to 512MB) if ones tries to start a partition with 256 MB?

[1] https://www-01.ibm.com/support/docview.wss?uid=isg2cb468b15654ca89b85257f7200746c16

[sreeteja (sreeteja)]

I tried to incorporate this
- Is rounding happening (up to 512MB) if ones tries to start a partition with 256 MB?

Then the instance is going to error state ...so seems like this statement given in the zHMCv2.13.1 pdf is valid..
The initial amount of memory to assign to the partition
when it is started, specified in MB. This value must be at
least 512, and it must be less than or equal to the value of
maximum-memory.

[sreeteja (sreeteja)]

I tried this by giving the creating a flavor with 500MB RAM and tried to use this to launch the instance

[sreeteja (sreeteja)]

The server could not comply with the request since it is either malformed or otherwise incorrect.<br /><br />
Jun 28 13:41:31 zfwcec140 nova-compute[7811]: Unable to update inventory for resource provider 1eb71e1c-b127-4fa6-9dec-3031bca1f4e6: Invalid inventory for 'MEMORY_MB' on resource provider '1eb71e1c-b127-4fa6-9dec-3031bca1f4e6'. The reserved value is greater than or equal to total.
Jun 28 13:41:31 zfwcec140 nova-compute[7811]: </body>
This is the error log that is generated when i tried to use max_memory as 512 in local.conf

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/479703
Committed: https://git.openstack.org/cgit/openstack/nova-dpm/commit/?id=37e2ca42158fb7683673eeae9518144868ebe97f
Submitter: Jenkins
Branch: master

commit 37e2ca42158fb7683673eeae9518144868ebe97f
Author: sreeteja <email address hidden>
Date: Mon Jul 3 13:37:11 2017 +0530

    Min value of max_memory is been added

    512mb is the minimum memory that is required to launch a partition and
    rounding off starts only from value greater that 512mb this decides the
    min value needs to be set to the config parameter max_memory.

    closes-Bug: 1689267

    Change-Id: I493fec40b412feb5303ab7ca9ee2f78c9b9220db