Beside Os.heap_bytes: malloc_zone_pressure_relief(NULL, 0) on macOS (weak, so a libc without it reads
0) and HeapCompact(GetProcessHeap(), 0) on Windows - kernel32 only, so the Windows build imports
nothing new; the bytes it says it released. Once after a load, never per frame.
Measured, for the record: on macOS it does NOT reach the large-block cache. A C program that frees six
15 MB blocks still holds 90 MB of MALLOC_LARGE (empty) after relief on every zone (it returns 0); only
MallocLargeCache=0 in the environment AT PROCESS START turns the cache off (read at malloc's init -
set later, it does nothing). Maroon Lake's watcher sets it for the processes it spawns.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>