Ceph » RADOS

We want to test with different values of osd_memory_target.
Also, create tests that necessarily go beyond the osd_memory_target limit.

Part 1: Test with a value of osd_memory_target lesser than the default, maybe half or less than that. This can be done by adding a new bluestore yaml fragment in qa/objectstore. This gets symlinked in a lot of places, so by doing this, we will be executing regular tests with the reduced value.

Part 2: Add a specific test that sets osd_memory_target to a lower value, and runs some kind of workload with thrashing. This test will also monitor how well the OSD does in keeping within the target memory value.
There are two ways to implement this:
1. by setting debug_bluestore 5/5 and looking for "the _trim_shards" and "_tune_cache_size" in the logs
2. or by polling for the heap stats via the admin socket command