The device-local tier of BufferPool only reused a buffer of the exact
size and usage it was asked for. Partial storage-image detiles and
retiles ask for a new size and the other transfer direction almost
every time, so the tier sat at its budget and missed and evicted
dozens of buffers per frame, and the vkFreeMemory calls on the release
thread held up submits and allocations on the recording threads.
Device-tier requests of 1 MiB and more now round up to an eighth of
their octave, the tier's buffers are created for storage and both
transfer directions, and a request takes the smallest retained buffer
from its own class up to twice its size. Host tiers, the budget and
eviction are unchanged. agc_buffer_pool covers the classes, the fit
and its bound, reuse only after release, the budget and the unchanged
lists.
Celegans12