The previous commit said the helper and the owner cleared the same huge
pages twice. Clean per-run page counters don't show that: with and without
the helper's heap mode a Sentry type check allocates the same number of
pages (1.07M). The cost is the page size: heap ranges the helper populates
before the owner advises them, and the partial huge pages at the ends of
each extension, stay on 4 KiB pages (Sentry 1816 instead of 1930 huge
pages, VS Code 2740 instead of 3051), next to the mmap-lock waits and the
smaller top pad. Also splits the THP-mode ternary to fit the line width.
Malte Ubl
9f6a11c3fe