With 1 GiB or less of free RAM, or 512 MiB or less of commit headroom, the
hard limit was exactly 0, so even a small file was refused with a message that
didn't say memory was low.
The reserve now shrinks with the measurement: up to a quarter of free RAM opens
automatically, the rest goes to approval, and an approved import always leaves
at least 256 MiB free. Limits are unchanged for automatic opening above 4/3 GiB
free and for approval from 4 GiB free. A refusal set by measured memory now
gives the free amount and says to close other apps and try again, and the
approval prompt warns when little memory would be left.
An unreadable cgroup still measures Some(0) and stays refused.
Khawar Zamman Wani
1ce1bced95