A bound buffer is joined across adjacent registered ranges only when every
one of them is larger than the 8 MiB window. PPSA25344's loading binds 16 MiB
and 4 MiB buffers whose backing was registered in two to six adjacent
pieces with the same access, some of them smaller than the window, so each
use of such a buffer was copied on the CPU: up to 348 GB in the first 300 s
of loading.
A bound buffer that starts at the first crossed range's start and ends at the
last one's end now joins those ranges whatever their size. A heap grown in
pieces matches that only for a binding over exactly its current pieces, so
growth beside a joined import does not re-import it. joinedCovers, used when a
joined import retires, accepts any adjacent run of ranges.
importJoinTests binds exactly over two 64 KiB pieces of a partly filled
window and requires one import of both; a binding across them that starts
inside the first piece stays apart.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ca95f74097