Consider ovsdb relay model to support memory trimming

[gujun4990]

Environment

ovs version: branch-2.16.2

Description

nb and nb-relay run in our environment, we found that they occupy amount of memory as below.

So we enable memory trimming to return unused memory to OS using below commands:

ovs-appctl -t /var/run/ovn/ovnnb_db.ctl ovsdb-server/memory-trim-on-compaction on
ovs-appctl -t /var/run/ovn/ovnnb_db.ctl ovsdb-server/compact

After that we can see that memory is down a lot as below.

But after a flew days, nb occupy amount of memory again as below.

After analyzing ovs code, we found that memory trimming will be executed when running ovsdb snapshot operation. Because relay model wouldn't run snapshot operation, so nb-relay wouldn't execute memory trimming even that it is enabled except that run ovsdb-server/compact command manually.
So whether we also need to consider ovsdb relay model to support memory trimming?