Address review on #6629:
- Cap the derived retention budget at a quarter of device capacity so a
large staged total cannot monopolize a small device; the multiplier
itself stays pending an instrumented target run.
- Log every release decision (reason, cached bytes, effective budget and
cap, staged total, free/total memory) and every staging OOM retry with
its staged byte total, so a single target run validates the headroom
multiplier directly.
- Make stager detach symmetric: set_cache_retention now shrinks the
previous cache's budget before growing the new one, so cache -> None ->
same cache counts the staged bytes exactly once (regression test added).
Signed-off-by: hsliuustc0106 <liuhongsheng4@huawei.com>
hsliuustc0106
c5295f3ffe