todo: memory_reclaim_for_tiered_storage

[C-mmon]

When memory is low, actively attempt to reclaim memory. calculate how much memory is needed based on the memory low limit and memory budget.

two attempt phase.
1st phase, entire needed memory
2nd phase, with the remaining gap.

[romange]

Hello @C-mmon . A nice suggestion. Have you stumbled upon this case? Do you have a scenario that triggers this path?

[C-mmon]

Hey @romange ,
I have not stumbled upon this. I currently want to contribute to dragonfly db, and going through all todo comments.
I can try writing some test case, where I can trigger this path but may require some help or suggestion.

[romange]

Yes, usually we add tests, writing tests is tricky, especially with tiering.
with tests we can debate what needs to be done and how.

[C-mmon]

Sure, I will work on the test and update the pull request.
Thanks